Feature/representor transitions

@mszenher or @asmith-mdsol Please review and merge.

This PR:
* adds enumerators associated with transitions and functionality to automatically include or exclude them by various options including state and transition conditions. 
* includes a module that allows the _Resource Descriptor_ state machine to hook into a state method on class or define a custom method if there is a naming conflict.

There is one pending spec, but this PR is large enough, so opted to put this up. Code coverage will be improved when that pending spec is completed.

All specs passing:

Finished in 3.35 seconds
208 examples, 0 failures, 1 pending
Coverage report generated (99.45%) covered.