Add ember-simple-auth, setup login

- Allow dropdown-buttons to render a partial

ember/config/environment.js

@@ -20,6 +20,10 @@ module.exports = function(environment) {
     }
   };
 
+  ENV['simple-auth'] = {
+    authorizer: 'authorizer:flarum'
+  };
+
   if (environment === 'development') {
     // ENV.APP.LOG_RESOLVER = true;
     // ENV.APP.LOG_ACTIVE_GENERATION = true;