Allow configurable ResourceController implementations.

This allows a different class to be specified to replace
PhlyRestfully\ResourceController when constructing controllers through
the factory.  A restriction is kept to ensure that the replacement
controller extends the original controller.

This allows users of PhlyRestfully to further configure the behaviour of
the controller if necessary.

* Modification to default configuration add a new "controllerClass"
  parameter, defaulting to the current ResourceController.
* Modification to the factory to construct the specified class instead
  the hard coded PhlyRestfully\ResourceController.
Merge pull request #86 from elyobo/configurable-controller-class

Allow configurable ResourceController implementations.
[#86] Key normalization

- underscore-separated keys, no camelCase
- test for existence of key before using it
[#86] Move controller_class to be per-resource

- Default should be the default; allow changing per controller.
[#86] Added documentation of controller_class config
[#86] Add test for new functionality

- Added test to verify that you can alter the controller class of
  individual resource controllers.
Fix CS issue in docs
Merge branch 'hotfix/86'

Close #86