Support basic authentification

[raspbeguy]

I've got a beets server behind a HTTPS Nginx reverse proxy with basic authentification setting. I cannot access it with the app, I tried to type the URL with the syntax https://user:password@server.tld.
On server logs, I can see it tried to log without any authentification items, resulting to a 401 error.

[maxammann]

Going to look into it. There is also another issue at the moment. A pending pull request: beetbox/beets#2050

[nico202]

Years later I added basic support for it. Password is saved in clear text but for me it's enough, see PR #4

[maxammann]

This has been implemented in PR #4 Thanks @nico202 :)