New Formula: Marsyas 0.4.7

[Marsyas](http://marsyas.info/) (Music Analysis, Retrieval and Synthesis for Audio Signals) is an open source software framework for audio processing with specific emphasis on Music Information Retrieval applications.

This Formula is marked `keg_only`, since it installs more than 30 commands, a few with dangerously short names, like `aim`, `ibt` or `kea`.

Originates from an academic background, with about [280 citations](http://scholar.google.com/scholar?cites=15038058367430590298&as_sdt=2005&sciodt=0,5) of the original paper (2000).