Filter Challenges on Search

[harmonherring]

Right now, performing a search sets/resets a timer every time you press a key. Once that timer expires the UI sends a query to the API for a new challenge list. What I'd like to do is to filter the displayed challenges from the ones stored in Redux and display those so that the search feels like it's in real-time. The API query should take place as usual and we should have some sort of non-blocking loading indicator while that's happening. The in-browser filter should filter using nearly identical criteria as the API/DB so that the results do not change once the query is finished, there will simply be more.