lyrics: Detect and follow redirected artist names in LyricsWiki

### Problem

Looks like the lyrics plugin does not know how to handle artist pages that are redirected. Ytcracker redirects to YTCracker, but when linking a song using the former capitalization it does not redirect properly. This could probably be partially an issue with Lyrics Wiki, since it seems like it'd make more sense for them to redirect instead.

Maybe the Lyrics plugin can somehow check the validity of the artist name afterwards if it fails?

Running this command in verbose (`-vv`) mode:

```sh
$ beet -vv lyrics the beginning ytcracker
```

Led to this problem:

```
lyrics: failed to fetch: http://lyrics.wikia.com/Ytcracker:The_Beginning (404)
```

### Setup

* OS: Archlinux
* Python version: 3.6
* beets version: 1.4.3
* Turning off plugins made problem go away (yes/no): N/A

My configuration (output of `beet config`) is: N/A

Start with the lyrics plugin path exercised by `beet -vv lyrics the beginning ytcracker` and inspect how the failed LyricsWiki URL is handled. Reproduce the `Ytcracker` 404 and determine whether redirect detection belongs in the plugin or LyricsWiki; done means the query reaches the `YTCracker` artist page instead of failing.

Written by the indexing model from the issue text.