Hg 91 top nav bar

This is the branch for the Wikia nav menu -- you tap the icon to the left of the Wikia icon, and it slides out. Both navigation and search are functional, and just need some touch-up.

**Update 08/27** -- Ember-side caching for search results in LocalWikiaSearchController. So far the cache stores 100 search API requests, and evicts the LRU result. I kind of rolled my own, and it works well afaik, but looking forwards it might be better to use a more Ember-centric approach with route transitions for query string strangs or something like that.

**TODOs**
For slide-out menu overall:
- [x] Why does Travis fail on the integration test _every time_ on this branch???
- [x] Make sure the 'x' button on the search bar is correctly clickable (it was acting up)
- [ ] If at all possible enforce a _13px_ margin between the search bar and 'Cancel' link while maintaining the 13px margins on the outer sides of both
- [ ] Comb through style, normalize style between search and nav (there probably is a better way of organizing the style files, as it is they are quite cumbersome)

For Navigation:
- [ ] Add sliding menus
 - [ ] Add cache of already-rendered menu panes
- [ ] Add touch states

For Search:
- Styling:
 - [x] Review styling overall
- Functionality:
 - [x] Internationalize messages (placeholder text, No Results/Loading... messages) 
 - [ ] Review nodejs-side search API design
 - [x] Reconcile node/initial page load changes with @hakubo's PR #111 

`topLevel` can be casted to ` NavItem`