Wrote tests showing how injection of Request into ResourceEvent should work

- Tests for ResourceEvent show injection, defaults, and nullability.
- Tests for RestController show that it should be injected by the time
  we call `getResource()`.
Inject Request into ResourceEvent

- Added first class `request` parameter to ResourceEvent, with setter
  and getter; value is nullable, and null by default.
- Altered ResourceEvent to override `setParams()`, allowing the request
  to be set via the composed "event params" in the Resource.
- Altered RestController to inject the composed request object into the
  Resource as an event parameter.
Merge branch 'feature/request-in-resource-event'

Inject the ResourceEvent with the MVC Request object.

Fixes zfcampus/zf-content-negotiation#13