Fix subtypes not working when using order_by

& refactor how we create new queries to prevent
this from happening again.
Bump version
Merge pull request #30 from johnnyg/fix-subtypes

Fix subtypes
Fix queries returning just the object id

which meant that subtype queries were being instantiated
as the parent class.
Make sure _types is included when querying subtypes

so that we can instantiate the correct subclass.
Bump version
Merge pull request #31 from johnnyg/fix-subtypes

Fix subtypes (again)