Only attach ApiProblemListener to API Controllers

If you need want to use ApiProblemListener in a non ResourceController
controller, have your controller emit `PhlyRestfully\RestfulJsonStrategy` or
attach the ApiProblemListener to your controller.

Signed-off-by: Michael Gooden <michael@bluepointweb.com>
Merge pull request #12 from MichaelGooden/hotfix/11-api-problem-listener

[Fix #11] Only attach ApiProblemListener to API Controllers
Merge branch 'hotfix/12'

Close #12
Fixes #11