Import refactor

Implements the package structure described in #5 

- Base classes in `hyp.base`
- `hyp.marshmallow` and `hyp.schematics` packages for integration with 3rd-party libs
- Removes `hyp.adapters` and `adapter_for`
- Bumps version in setup.py -> 0.6.0
- As per the PyPA's recommendation, use setuptools over distutils: https://packaging.python.org/en/latest/current.html#packaging-tool-recommendations