Enhanced assignee selector

https://www.agileplannerapp.com/boards/173808/cards/8121

In user research sessions an obvious improvement to the task of finding a name amongst the long list of assignees (when filtering publications) is to make that list searchable. Select2, which was already being used, can do this out of the box.

* Switch select2 to pull assets from a gem
* Remove unused image and script assets already provided by admin gem
* Bump jasmine gem and admin gem
  * Fix alignment of business support checkboxes
* Switch user filter to use select2

## Before
![screen shot 2014-11-06 at 12 29 48](https://cloud.githubusercontent.com/assets/319055/4935842/a9573090-65b1-11e4-926b-f0d397695554.png)

## After
![screen shot 2014-11-06 at 12 30 03](https://cloud.githubusercontent.com/assets/319055/4935841/a95334ea-65b1-11e4-9618-df2d2760a9cf.png)