Update imports in tests

[no ci]
Remove adapters/base.py and rename responder.py -> base.py
Update dev requirements

test against newest versions of marshmallow and schematics
[no ci]
Implement new package structure

See #5
Raise NotImplemented error if ADAPTER not defined on Responder

Also update README example
Use setuptools rather than distutils
Merge pull request #9 from sloria/import-refactor

Import refactor