Bump client version to 0.2.0

Make invalid bit length error handling consistent between secrets and
orders
Fixed a bug involving secret expiration dates
Add the skeleton for keep_test, and make a small change to client_test
Bump client version to 0.2.1
Change setup.py so that it reads the version from version.py
Merge pull request #13 from Aghoreyshi/master

Fix a bug and add the skeleton for keep's unit test