Merge pull request #22 from thallgren/feature/binder

Add unit tests (and some bug-fixes) to the Pops::Types.
w.i.p binder
Merge remote-tracking branch 'hlindberg/feature/binder' into feature/binder
Make type calculator infer PType for types and PType

The infer method did not handle inference of a type (it resulted
in a Ruby type with reference to the type class).

This commit updates the type calculator with an infer of PObjectType.
This means that all types, including the meta-type PType is typed
as PType. Tests added.

(This is all esoteric, but needs to be done correctly).
Add infer_Class to remove requirement to pass an instance.

Without this it is more difficult to create a type for a class.
Add skeleton of BindingsChecker.

This adds w.i.p on a BindingsChecker - a validator of a bindings
model. It contains:
- Issue module
- Checker/Validator
- TypeFactory method to create a PCollectionType (used in checker)
- Additions to Bindings model (multibind producers)