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- Allow empty list/dict as json object (GH-100).
- Added `response_callback` (GH-151).
- Added ``Response`` interfaces (GH-155).
- Fixed unicode characters in querystring (GH-153).
- Added support for streaming IO buffers (GH-154).
- Added support for empty (unset) Content-Type (GH-139).
- Added reason to mocked responses (GH-132).
- ``yapf`` autoformatting now enforced on codebase.