extract Event.search_tag to prep for some major method moving.
move search related methods from Event to Event::Search.
inline some private Event::Search methods.
refactor Event::Search#grouped_events.
refactor Event::Search#grouped_events and #events.
clean up associated tests after refactoring Event::Search and Event.
simplify EventsController#search spec.
Merge pull request #111 from botandrose/event_search_cohesion

Event::Search cohesion