Payasan

I've rebooted development on Payasan. The current implementation is completely new as I've decided that round-tripping through a subset of ABC (hopefully LilyPond later) is due to be Payasan's salient feature.

Quasiquoting ABC affords a very concise input syntax, outputting ABC generates immediate feedback - for instance if I applied a transposition to the input notelist, I will be able to see it's effect in the notated output I won't just have to trust my ears.