refactor(ionicNamespace): create window.ionic

Build processes may also be using the window.ionic object, but it’ll
have to create its own because ionic.js may not have run yet. Use the
existing window.ionic obj if it exists, otherwise create it.

Author: adamdbradley

js/ionic.js

@@ -1,8 +1,6 @@
 
-// Create namespaces
-//
-window.ionic = {
-  controllers: {},
-  views: {},
-  version: '<%= pkg.version %>'
-};
+// Create global ionic obj and its namespaces
+// build processes may have already created an ionic obj
+window.ionic = window.ionic || {};
+window.ionic.views = {};
+window.ionic.version = '<%= pkg.version %>';