Add optional recursive camelization of keys
Merge branch 'convert_keys' into rushplay

Conflicts:
	lib/active_model/convertable.rb
	lib/active_model/serializable.rb
	lib/active_model/serializer.rb
	test/fixtures/poro.rb
	test/unit/active_model/serializer/convertable_test.rb
Add back root
Add back root and remove accidentally committed code