Add docstrings for API method of g.datastore.key.Key.
Incorporate feedback from @dhermes.
Incorporate feedback from @dhermes.
Making datastore.connection.Connection inherit from base Connection.

Fixes #197.
Merge pull request #184 from tseaver/add_key_docstrings

Add docstrings for API method of g.datastore.key.Key.
Merge pull request #198 from dhermes/datastore-cnxn-inherit-generic

Making datastore.connection.Connection inherit from base Connection.