Add application helper for unordered lists

* Helper method renders partials in a ul for each item in a collection
* Refactor views to use this helper method
Extract partial for rendering a tag

* Tell git not to ignore app/views/tags (whoops!)
* Add tags show view to git
Allow some actions when not signed in

* Add before actions to controllers
* Require login before creating, updating, or deleting a resource
* Allow users to view resources when not logged in
* Update some views based on whether a user is logged in or not