Having a `write()` method on a `Song` object is weird

[emkay]

We have song.done() and song.write(). When done() is called we are saying that this song is done and anything that we need to do to finish up constructing the song can now be done. The write() method makes the build directory and outputs the assembler for the sound engine and the song. The reason it needs to be two different calls is that it is possible for you to produce multiple songs. This makes the api confusing because you are calling song.write() not songs.write().

A couple ideas:

• make a Songs object that is a collection of songs and put the write() method there
• do not allow multiple songs, and have a single song restraint per file/program