Add pagination to posts listing

* Add backbone-pageable plugin and use this to page the Posts collection
* Add handlebars-pagination helper
* Make pagination links dynamic
* Add events for changing page to the PostListView
Add 'total_count' to posts API - used in pagination
Update posts pagination with real totalRecords state

* use total_count from json in collection's parseState
* Trigger re-render of pagination on add/remove/reset of collection
  May not be the most efficient way to do this.
Prevent paging past first/last pages
Wiring post sorting and page count UI
Allow sorting posts by 'updated' field
Update "Showing x-y of z posts" text based on paging

* Move listing info text into a partial template
* Update this html when we update pagination
* Compile pagination and post list info template when view is loaded,
  not when ever they're rendered.
* Add type='info' to paginate helper
Fix coding style issues in PostListView.js
Fix coding style on typecasting in Posts Api Controller
Merge pull request #92 from ushahidi/posts-paging

Wire up posts paging/sorting/page count UI