Add Deezer support

[Pan6ora]

Hello,

Very interested by your project. I think it is one of these services that "needs to" exist. As a Deezer user I would be happy to help adding this service.

As I don't have that much time to dig into your code, maybe you could point me out the useful stuff needed to add such a service ? I'm thinking about the list of classes and methods needed (with their in/out data). Thus I would be able to start playing with some deezer-python API.

Waiting for your answer I will start to but my hands in the code.

[platers]

Thanks for the interest! I just added a beatsaber service, you can look at these commits to see what needs to be changed. The Spotify service is likely very similar to Deezer.

The rough steps are:

1. Create test_deezer.py in test_lib. Test functionality once its written
2. Add deezer URIs to uri.py
3. Write deezer.py. Implement the protocols in service.py one by one.