Flask-jwt-extended

* Default to the Flask JSON encoder and allows for custom JSON encoders for encoding JWTs (139)

* Fixes a CSRF error when using jwts in cookies and the `jwt_optional` decorator (129)

In this release, we are no longer toggling the flask `PROPAGATE_EXCEPTIONS = True` setting in this extension. It was set in here initially to get things working with `flask-restful`, but setting a global flask option in here just so that it would work with another flask extension was a poor design choice.

Note that if you are using flask-restful (or possibly other extensions) and the error handlers stop working after this update, you will need to manually set the `PROPAGATE_EXCEPTIONS` setting in your configuration to keep everything working. Sorry all the inconvenience.

* Removed `PROPAGATE_EXCEPTIONS` setting from this extension
* Internal cleanup and refactoring

* `jwt_required` (et al) no longer require authorization to be present on an `OPTIONS` request (119)
* Add `Add Werkzeug>=0.14` to install requirements (115)

* Adds ability to use the `samesite` cookie attribute (34, 113, 115). Requires Werkzeug >= 0.14. Thanks farshiana!

* Exports `get_csrf_token` to the api (112)