Feature/filter search

Hey guys,

Sorry this one took a little longer than I expected to wrap up.

* Added a search filter to the dashboard and groups show pages
* Filter will show a paginated list of all discussions that match the search query, with 10 results per page
* Filter discussions based on title query for now - improvements to be made later include full text search with a new 'results' page

@jonlemmon The javascript code here is probably pretty bad. I wasn't exactly sure what to do with the duplication between the groups and dashboard js files. Maybe you have some ideas for this now? Or I can refactor it in another request.

Have added some cukes as well - hopefully these are all good. 

Let me know your thoughts.