fix(cli): use github for default gulpfile

Rawgit permanently caches the file, so it doesn't update, which was the
whole point of using github.  Just use github directly, as probably not
too many people will need to upgrade their v2 projects and this will
eventually be removed anyways.

Author: tlancina

lib/cli.js

@@ -252,7 +252,7 @@ function downloadDefaultGulpfile(){
   var deferred = Q.defer();
   var project = IonicProject.load();
   var branch = project.get('typescript') ? 'typescript' : 'master';
-  var url = 'https://cdn.rawgit.com/driftyco/ionic2-app-base/' + branch + '/gulpfile.js';
+  var url = 'https://raw.githubusercontent.com/driftyco/ionic2-app-base/' + branch + '/gulpfile.js';
 
   console.info(('Downloading default gulpfile from: ' + url));