Convert from roman to chord

[titus-ong]

Add method to convert from roman notation to a Chord in the ChordRomanConverter class.

[titus-ong]

Possibly copy over the chord's quality, add, bass when creating Roman. This would make restoring to chord easier since we can create a new chord from all these attributes.

[titus-ong]

May become irrelevant if new architecture (#39) for Chord class contains Roman attribute, i.e. they do not need to be converted.