WIP: migrate the sidebar partials to AngularJS.
Simplified the partial that shows the "all subscriptions" folder.
Minor reorganization in the markup of layouts and header partial.

The opening <html> tag is rendered in the layout files instead of the header partial now. This makes more sense because the closing </html> tag is in the layout files.
Moved the angular js file link, ng-app and ng-controller directives so that the whole application is an angularjs app.

This does not include devise views, which do not use angularjs.
WIP: migrate unsubscribe feed functionality to angularjs.