Watch Providers

[lardbit]

This PR adds functionality for the Watch Providers endpoints:

• https://developer.themoviedb.org/reference/watch-providers-available-regions
• https://developer.themoviedb.org/reference/watch-providers-movie-list
• https://developer.themoviedb.org/reference/watch-provider-tv-list

Unit test are included as well:

python -W ignore:ResourceWarning -m unittest tests.test_watch_providers

Usage:

import tmdbsimple as tmdb
watch_providers = tmdb.WatchProviders()
watch_providers.watch_providers_available_regions()
watch_providers.watch_providers_movie_list()
watch_providers.watch_providers_tv_list()

[lardbit]

@celiao are you still accepting PRs?