Command line client --blacklisted-return-code option (#46)

Fixing unit tests (#43)

* Workaround for bytecode URLs at py3
* Adding tox.int
* Cleaning up the code

Fix key error in fh_response (#40)

* update gitignore for PyCharm, venvs and ctag file
* fix in sync_full_hashes for response without matches

Cosmetic changes: docstrings formatting

Workaround for negative sleep interval

Make sure journal mode is set before DB init

Refactoring for more coherent transaction management

Disable Google API cache discovery which does not work with recent oa…

…uth client library

Specify google-api-python-client dependency version

Performance and code optimizations; Cache schema versioning