Tidies readme and thing unit test ready for next bit of work.
Let's Ability worry about validity of abilities
Allows abilities to be set by defining a method on the thing, that returns an entity.id
Merge remote-tracking branch 'original/develop' into develop

* original/develop:
  Allows abilities to be set by defining a method on the thing, that returns an entity.id
  Let's Ability worry about validity of abilities
  Tidies readme and thing unit test ready for next bit of work.