Specify that CSS, JS, and Ruby can be embedded in ERB

This allows the fix attempted in #224 to still work while also
supporting proper ERB comments

Author: wingrunr21

package.json

@@ -354,7 +354,12 @@
       {
         "language": "erb",
         "scopeName": "text.html.erb",
-        "path": "./syntaxes/erb.cson.json"
+        "path": "./syntaxes/erb.cson.json",
+        "embeddedLanguages": {
+          "source.css": "css",
+          "source.js": "javascript",
+          "source.ruby": "ruby"
+        }
       },
       {
         "language": "gemfile",