Add Reddit Playlister support, separate parsing/utility functions

Added scrobbling support for the [Reddit Playlister](http://redditplayer.phoenixforgotten.com).

In the course of doing so, I found that the artist/track parsing functions were replicated in both soundcloud.js and youtube.js and that they would be useful for the Reddit Playlister as well, so I moved them to a common file so they can be used more easily for future website scrobblers.