Jwplatform

------------------

- Added support for JWPlatform file upload using a multi-part mechanism.

------------------

- Fix a bug on generating the signature when array value is in the query string.

------------------

- Added support for JWPlatform API v2
- All existing v1 API functionality has been moved to the jwplatform.v1 submodule (from jwplatform).

------------------

- remove Python 2 compatibility

------------------

- parameters are now included in the request body by default for POST requests

------------------

- improved default parameters handling when instantiating client
- added exponential connection backoff