First version of chord parser and fingering dictionary

OK, so here's the first version of the chord parser service and fingering dictionary. Sorry it's such a big PR; I'll add some comments in GitHub to explain what's going on.

First off, there's this standalone library thing I made: https://github.com/nolanlawson/chord-magic.

Second: if you load this thing in the browser, you'll now see this message in the console:

```
Hey what are the fingerings for the chord of C?
["x32010", "x35553", "x35553", "x35553", "x30010", "032010", "035553", "332010", "3x2010", "x32010", "x35550", "xx45x0"]
```

So clearly we have way too many variations on the same chord, but I guess having too many is better than having too few! Also there are a few duplicates; we should fix those later.