changed Mode to accept keyword arguments for new Mode.  added spec for Mode
add == specs to Juicy::Mode
add to_s specs to Juicy::Mode
refactor play_concurrently along with taking out old comments
clean up code here and there, take out trailing spaces, improve scale specs
extract comments into descriptive blobs in front of methods to clean up code
delete trailing spaces, DI, abstract mode selection
implemented first melody generation algo