v2.2.0

Improvements:

• PerformanceWarning will be issued when Python-Redmine does some unnecessary work under the hood to fix the clients code problems

Changes:

• Backwards Incompatible: Removed vendored Requests package and make it an external dependency as Requests did the same with it's own dependencies
• Backwards Incompatible: Removed Python 2.6 and 3.3 support as they're not supported by Requests anymore

Bugfixes:

• Redmine.upload() fails under certain circumstances when used with a file-like object and it contains unicode instead of bytes (Issue #216)
• Redmine.session() doesn't restore previous engine if fails (Issue #211) (thanks to Dmitry Logvinenko)