CI tests and tests with specific Django version

mislavcimpersak commented 5 years ago

added .travis.yml config file (maintainer still needs to turn the switch on in Travis CIs interface)
- passed builds can be seen here: https://travis-ci.org/mislavcimpersak/dj-nexmo
dropped Python 3.3 since in 2017 it reached end-of-life
- also, finding just the right packages that work with py3.3 can be a daunting task
using Travis matrix to test different combos of Python and Django
added testing for Python 3.7 support
fixed marshmallow version because newer marshmallow is throwing errors (using a newer package should be fixed in another PR)
~fixed nexmo version because newer nexmo is throwing errors (using a newer package should be fixed in another PR)

mislavcimpersak commented 5 years ago

@judy2k Any chance of getting this reviewed? 😁

I can provide more explanation if needed

judy2k commented 5 years ago

This was a fantastic PR. Thank you so much!

Nexmo / dj-nexmo