chore(broccoli): Load different env config files

Fix angular#899
Close angular#913

Author: petarblazevski

lib/broccoli/angular2-app.js

@@ -393,8 +393,14 @@ class Angular2App extends BroccoliPlugin {
    * @return {Tree} The config files tree.
    */
   _getConfigTree() {
-    const isProduction = loadEnvironment(this.project).production;
-    var envConfigFile = isProduction ? 'environment.prod.ts' : 'environment.dev.ts';
+    let env = process.env['EMBER_ENV'] || 'dev';
+
+    switch (env) {
+    case 'production': env = 'prod'; break;
+    case 'development': env = 'dev'; break;
+    }
+
+    var envConfigFile = `environment.${env}.ts`;
 
     return new BroccoliFunnel('config', {
       include: [envConfigFile],