Coords

This release uses a two dimensional coord plane for representing notes and intervals (and thus also chords). This abstracts the representation of a note (and a interval) from its string name and will make it easier to implement different string interfaces (for different note names), implement microtonal temperaments and also simplifies the code a lot!

Because of the transition from string representation to coords, many properties of both the TeoriaNote, TeoriaInterval and the TeoriaChord objects, have been translated to methods. Take a look at the docs (in the README) to familiarise yourself with these changes.