Add Last.FM integration

I've made a few changes here:
1. Added Last.FM integration so that users can quickly search for the Artist/Album/Track on Last.FM
2. Changed up the UX for "show new tracks" vs "show all tracks", so that it is more transparent.
4. Fixed typos.
5. If we want people to keep contributing to this project, we need to give fair credit. I made some subtle changes to make the project more contribution-friendly.