New formula: Marsyas

MARSYAS is a software framework for rapid prototyping of audio applications, with flexibility and extensibility as primary concerns.

It is used a lot in [Music Information Retrieval](https://en.wikipedia.org/wiki/Music_information_retrieval) and it's a bit tricky to install correctly, so my hope is that with this formula people in my field will be able to install the latest development version with no hassle.