Rewriting scale(note, scale_name) in a more beautiful way

Removed duplicated code
Extracted data structure to make it easier to reuse if required
Fixed trailing whitespaces
Merge pull request #3 from SylvainDe/master

Rewriting scale(note, scale_name) in a more beautiful way
Sylvain added to contributors
Merge remote-tracking branch 'upstream/master'

Conflicts:
	README.md
	musthe/musthe.py