Added
* Request validation with Marshmallow schemas
* API Explorer under /api-explorer
* edit and delete message API's
Changed
* **[breaking] 0.6 BRANCH IS THE LAST RELEASE THAT SUPPORTS PYTHON OLDER THAN 3.6**
* Demos are now standalone applications
* Uses itsdangerous 1.1.0 for signing, to support 0.24 version additional
config option `validate_requests` to allow disabling timestamp checks