Traceur and Babel file URL fix on Windows (#342)

Author: guybedford

index.js

@@ -2,15 +2,15 @@ var System = require('./dist/es6-module-loader.src');
 
 System.transpiler = 'traceur';
 try {
-  System.paths.traceur = require.resolve('traceur/bin/traceur.js');
+  System.paths.traceur = 'file:' + require.resolve('traceur/bin/traceur.js');
 }
 catch(e) {}
 try {
-  System.paths.babel = require.resolve('babel-core/browser.js');
+  System.paths.babel = 'file:' + require.resolve('babel-core/browser.js');
 }
 catch(e) {}
 try {
-  System.paths.babel = System.paths.babel || require.resolve('babel/browser.js');
+  System.paths.babel = System.paths.babel || 'file:' + require.resolve('babel/browser.js');
 }
 catch(e) {}