Codable Conformance

[maksutovic]

          @maksutovic @aure since we're taking a look at this PR I just wanted to keep applying pressure on Codable here.

The raw value of our ChordType is a String. If you were to change the name of a ChordType enum case in the future then you would break the decoding of any encoding of that case that you have previously made.

IMO if we are set on introducing Codable conformances, we should use some stable raw value when we do it - such as explicitly assigning each case to a specific integer value.

Originally posted by @Matt54 in #47 (comment)

I completely agree that coddle conformance needs to happen, I'll work on it this weekend