Add Last.FM integration

[hdmchl]

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.
3. Fixed typos.
4. 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.

[hdmchl]

You know what, I think we can make the "Play/Pause => Show notification" preference clearer. I made a general change, but I just realised, I kind of got rid of the play-pause feature.

Let me have another go at that... brb

[citruspi]

Hey @hadimichael,

This is some great stuff, but I'd appreciate it if you could split the different changes (i.e. Last.fm integration, UX changes, typo fixes, fair credit, etc.) into separate pull requests.

— @citruspi

[hdmchl]

Fair call.

Edit: Hey @citruspi because the changes I made are not entirely sequential and were all done on master (oops), it's going to be tricky to break it all up. I tried branching it, but it got very messy. I'm open to suggestions, but it looks like it's going to have to come through in one request. Sorry mate.

[citruspi]

@hadimichael,

Hmm, I'll take a look at the commits tomorrow and figure out a good way to handle it. I'll reopen this pull request for now.

Either way, thanks for contributing.

— @citruspi

[hdmchl]

Cool. Thanks. I also went back and fixed up that Preferences change I made. Check out the newest commits here. https://github.com/hadimichael/Spotify-Notifications/commits/master

I can include those in a separate pull-request, immediately after this one goes through.

[hdmchl]

Any changes here?

[citruspi]

@hadimichael,

Not yet, but I do plan to merge the changes. I've just been busy, last week with projects, and this week with PyCon.

Before merging, I just want to actually go through and read the changes to the code.

However, I do have one change I'd like made before I'll merge.

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.

I don't particularly care that you removed my name from it, as I planned to do that anyway, but I disagree that linking to the Contributor Graph is the best way to give fair credit. In the past, I've seen that it takes some time for someone to appear on the Graph, and sometimes they never do. I think that instead you should link to the contributors.md file (located here) which allows people who have contributed in ways other than pull requests to be recognized.

Thoughts?

— @citruspi