Add initial pass at writing actual json output

[ryanwersal]

Restructure library code to try to open a path towards spreading out functionality across several modules.

Adds mutagen to read ogg file metadata to help with populating several values in the json files.

With regards to the library restructuring - a couple of my thoughts:

• I'm not a huge fan of using classes/objects in Python aside from using them as a typed way of packaging data (which is how I feel I used BeatSaberSong in this change).
• I prefer functions largely because testing them is easier since you don't need to get the full class setup to do the test (particularly if the function is pure).
• This also helps since we spread out the functionality across files/modules.

Thoughts?

[ryanwersal]

Should close #10