docs(developer): add developer notes and fix karma local run

Add very basic developer notes on how to test and submit changes.

Fix the license info at the end of README.md.

Fix the local karma config so it actually runs firefox.

Closes #285

Author: juliemr

Diff for: DEVELOPER.md

@@ -0,0 +1,21 @@
+Submitting Changes
+------------------
+
+Do NOT submit changes to the built files in the `dist` folder. These are generated before
+releases.
+
+
+To run tests
+------------
+
+Make sure your environment is set up with:
+
+`npm install`
+
+In a separate process, run the WebSockets server:
+
+`node ./test/ws-server.ts`
+
+Run the tests using Karma:
+
+`npm test`

Diff for: README.md

@@ -308,4 +308,4 @@ zone.run(function() {
 
 
 ## License
-Apache 2.0
+MIT

Diff for: karma.conf.js

@@ -15,6 +15,7 @@ module.exports = function (config) {
 
     plugins: [
       require('karma-chrome-launcher'),
+      require('karma-firefox-launcher'),
       require('karma-jasmine'),
       require('karma-sourcemap-loader'),
       require('karma-webpack')