updated license and contributing

Author: liabru

Diff for: CONTRIBUTING.md

@@ -1,4 +1,10 @@
-### Building and Contributing
+# Contributing
+
+## License Agreement
+
+When providing any contributions, you must agree and be legally entitled to provide them for use and distribution in the project under the same terms as the [license](https://github.com/liabru/matter-js/blob/master/LICENSE), otherwise they can not be accepted.
+
+## Building
 
 To build you must first install [node.js](http://nodejs.org/) and [gulp](http://gulpjs.com/), then run
 
@@ -8,8 +14,10 @@ This will install the required build dependencies, then run
 
 	gulp dev
 
-which is a task that builds the `matter-dev.js` file, spawns a `connect` and `watch` server, then opens `demo/dev.html` in your browser. Any changes you make to the source will automatically rebuild `matter-dev.js` and reload your browser for quick and easy testing.
+which is a task that builds the `matter-dev.js` file, spawns a development server and opens `http://localhost:8000/demo/index.html` in your browser. Any changes you make to the source will automatically rebuild `matter-dev.js` and reload your browser.
+
+## Contributions
 
-Contributions are welcome, please ensure they follow the same style and architecture as the rest of the code. You should run `gulp test` to ensure `eslint` gives no errors. Please do not include any changes to the files in the `build` directory. 
+Contributions by pull request are welcome! Please ensure they follow the same style and architecture as the rest of the code. You should run `gulp test` and ensure there are no reported errors. Please do not include any changes to the files in the `build` directory. All contributors must agree to the license agreement described at the beginning of this document.
 
-If you'd like to contribute but not sure what to work on, feel free to message me. Thanks!
+If you'd like to contribute but not sure what to work on, feel free to get in touch.

Diff for: LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2014 Liam Brummitt
+Copyright (c) Liam Brummitt and contributors.
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

Diff for: src/body/Body.js

@@ -626,6 +626,7 @@ var Axes = require('../geometry/Axes');
      * @return {}
      */
     var _totalProperties = function(body) {
+        // from equations at:
         // https://ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=st&chap_sec=07.2&page=theory
         // http://output.to/sideway/default.asp?qno=121100087
 

Diff for: src/core/Common.js

@@ -279,7 +279,7 @@ module.exports = Common;
     };
 
     var _seededRandom = function() {
-        // https://gist.github.com/ngryman/3830489
+        // https://en.wikipedia.org/wiki/Linear_congruential_generator
         Common._seed = (Common._seed * 9301 + 49297) % 233280;
         return Common._seed / 233280;
     };
@@ -411,7 +411,9 @@ module.exports = Common;
      * @return {array} Partially ordered set of vertices in topological order.
      */
     Common.topologicalSort = function(graph) {
-        // https://mgechev.github.io/javascript-algorithms/graphs_others_topological-sort.js.html
+        // https://github.com/mgechev/javascript-algorithms
+        // Copyright (c) Minko Gechev (MIT license)
+        // Modifications: tidy formatting and naming
         var result = [],
             visited = [],
             temp = [];

Diff for: src/geometry/Svg.js

@@ -151,6 +151,9 @@ var Bounds = require('../geometry/Bounds');
 
     var _svgPathToAbsolute = function(path) {
         // http://phrogz.net/convert-svg-path-to-all-absolute-commands
+        // Copyright (c) Gavin Kistner
+        // http://phrogz.net/js/_ReuseLicense.txt
+        // Modifications: tidy formatting and naming
         var x0, y0, x1, y1, x2, y2, segs = path.pathSegList,
             x = 0, y = 0, len = segs.numberOfItems;
 

Diff for: src/geometry/Vertices.js

@@ -150,7 +150,7 @@ var Common = require('../core/Common');
             j;
 
         // find the polygon's moment of inertia, using second moment of area
-        // http://www.physicsforums.com/showthread.php?t=25293
+        // from equations at http://www.physicsforums.com/showthread.php?t=25293
         for (var n = 0; n < v.length; n++) {
             j = (n + 1) % v.length;
             cross = Math.abs(Vector.cross(v[j], v[n]));
@@ -354,6 +354,7 @@ var Common = require('../core/Common');
      */
     Vertices.isConvex = function(vertices) {
         // http://paulbourke.net/geometry/polygonmesh/
+        // Copyright (c) Paul Bourke (use permitted)
 
         var flag = 0,
             n = vertices.length,
@@ -396,7 +397,7 @@ var Common = require('../core/Common');
      * @return [vertex] vertices
      */
     Vertices.hull = function(vertices) {
-        // http://en.wikibooks.org/wiki/Algorithm_Implementation/Geometry/Convex_hull/Monotone_chain
+        // http://geomalgorithms.com/a10-_hull-1.html
 
         var upper = [],
             lower = [], 
@@ -411,7 +412,7 @@ var Common = require('../core/Common');
         });
 
         // build lower hull
-        for (i = 0; i < vertices.length; i++) {
+        for (i = 0; i < vertices.length; i += 1) {
             vertex = vertices[i];
 
             while (lower.length >= 2 
@@ -423,7 +424,7 @@ var Common = require('../core/Common');
         }
 
         // build upper hull
-        for (i = vertices.length - 1; i >= 0; i--) {
+        for (i = vertices.length - 1; i >= 0; i -= 1) {
             vertex = vertices[i];
 
             while (upper.length >= 2 

Diff for: src/module/license.js

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  * 
- * Copyright (c) 2014 Liam Brummitt
+ * Copyright (c) Liam Brummitt and contributors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal