this should work
Add ArrayTypecaster

- Makes the previous commit's (a4b697f) test pass
- This should be useful for pretending to have relations: Store a bunch of
  ActiveAttr::Models in an attribute and have it default to [], for example
Add more documentation for ArrayTypecaster

- Add @since
- Add class documentation
- Add param to method call
Merge remote-tracking branch 'calebthompson/array-typecaster' into array-typecaster

Conflicts:
	lib/active_attr/typecasting.rb
bad merge. fixing
added tests for array typecaster. added ability to pass in array serialized to JSON
add a hash typecaster
Merge branch 'hash-typecaster'