Telesign

- Added support for application/json content-type

- Fix bug where HTTP GET calls were not including query parameters

- Re-brand Auto Verify to App Verify and refactor associated names

- updated and improved README
- secret_key refactored to api_key to align with docs and portal
- api_host is now known as rest_endpoint to align with docs and portal
- fixed python3.x bug with bytes vs str in verify_telesign_callback_signature
- various doc string updates and fixes
- removed requests specific config, subclass and customize instead
- added travis CI, codecov coverage and additional unit tests

- Major refactor and simplification into generic REST client.
- API parameters are now passed as kwargs to endpoint handlers.
- Now using Requests sessions correctly.
- UserAgent is now set to track client usage and help debug issues.
- generate_telesign_headers is now static and easily extracted from the SDK if
custom behavior/implementation is required.

- Added PhoneId number_deactivation endpoint.