Fixed CSP Strict Style Compatibility

Fixes plotly#2355 Plotly uses inline CSS

* Providing switch in build process to enable CSP strict style build
* Creating a static CSS file at command line provided path defaulting to build folder with name plot-csp.css

Author: shaurya-sisodia

package.json

@@ -28,7 +28,7 @@
     "schema": "node tasks/schema.js",
     "stats": "node tasks/stats.js",
     "find-strings": "node tasks/find_locale_strings.js",
-    "preprocess": "node tasks/preprocess.js",
+    "preprocess": "node tasks/preprocess.js %npm_config_cspNoInlineStyle% %npm_config_pathToCSS%",
     "use-draftlogs": "node tasks/use_draftlogs.js",
     "empty-draftlogs": "node tasks/empty_draftlogs.js",
     "empty-dist": "node tasks/empty_dist.js",

tasks/preprocess.js

@@ -21,8 +21,17 @@ function makeBuildCSS() {
     }, function(err, result) {
         if(err) throw err;
 
-        // css to js
-        pullCSS(String(result.css), constants.pathToCSSBuild);
+        var cspNoInlineStyle = process.argv[2];
+        var pathToCSS = process.argv[3] || 'plot-csp.css';
+        if(cspNoInlineStyle) {
+            // if csp no inline style then build css file to include at path relative to build folder
+            fs.writeFile(constants.pathToBuild + pathToCSS, String(result.css), function(err) {
+                if(err) throw err;
+            });
+        } else {
+            // css to js
+            pullCSS(String(result.css), constants.pathToCSSBuild);
+        }
     });
 }