Refactored test reporters; Fixed Test Bundle Reporter output

Addresses story: https://www.pivotaltracker.com/story/show/60537766

Changes:
 - Moved all test reporters to reporters group
 - CDRExampleBase tracks runTime via startDate and endDate
 - Added new methods for CDRExampleReporter as an alternative to KVO:
   - runWillStartExample:
   - runDidFinishExample:
   - runWillStartExampleGroup:
   - runDidFinishExampleGroup:
   - runWillStartSpec:
   - runDidFinishSpec:
   These methods allow more than just observing when state changes: such
   as timing information. KVO-ing the state property is still acceptable.
 - CDRReportDispatcher wraps cedar's interaction to reporters to
   support the new public protocol methods.
 - Test bundle reporter now reports tests as they start and end.
 - Test bundle reporter no longer uses an explicit date formatter over -[NSDate description].
 - Fixed test bundle reporter from failing to finish all its suites for Xcode output
 - Fixed test bundle reporter emits Xcode test method format as "-[SpecClass describe_and_contexts_it_string]". It drops the SpecClass string from the test method name if prefixed (to shrink output based on the spec template).
 - Backfilled test bundle reporter tests.
 - CDRExampleBase's run method is now runWithDispatcher: