Moving a constant definition
Crafting alternate method signature

I want PolicyEnforcer.enforce! to take multiple objects
Replacing enforce! with enforce_take_two!

This is an interrim step
Restoring usage of #enforce!
Adding README for policy_enforcement
Adding TODO question regarding PolicyEnforcer

[skip ci]
Tidying up README

[skip ci]
Updating README.md

Adding links in the README to the various modules
Renaming presenters to decorators

To better reflect how they are named by Draper I'm moving these to
app/decorators
Adding specs for Permission
Renaming :subject to :entity
Merge pull request #23 from ndlib/replacing-subject-with-entity

Renaming :subject to :entity