added some Info to AudioSummary & additional SearchParams

Added "new" Echonest API features to libechonest.

Relate BlogPosts about Echonest API: http://blog.echonest.com/post/53511313353/new-audio-attribute-acousticness & http://musicmachinery.com/2011/11/04/speechiness-is-it-banjo-or-banter/

Maybe more stuff to come (so pls don't yet bump the version of libechonest) beginning of July if I figure out how to reliably find out what is always included in AudioSummary of echonest