Hot Code Reloading for development purpose and Travis Test build

[dlesz]

Features added:

• Separate compose docker-compose.development.yml for hot code reloading with Flask server and watchdog,. HOW TO Instructions added to README.md
• Travis test build. .travis.yml

Contributing to Twilio

All third-party contributors acknowledge that any contributions they provide will be made under the same open-source license that the open-source project is provided under.

• I acknowledge that all my contributions will be made under the project's license.

[mattkohl]

this is great!

[dlesz]

this is great!

Thanks mattkohl and thanks to you for the great effort. I did not notice the github actions workflow on your master branch until now. Makes the .travis.yml a bit redundant😊 Also, feel free to ditch the health_check() method in app.py.