adding __composer_type member to every composer class. great for debugging certain things (ie what the hell did i just console.log?)
yet another sort_index bugfix. YAHHH!
adding some performance benfits to filtercollections change event monitoring. you have to explicitely turn off `refresh_on_change` but once you do, instead of doing a brute-force refresh on every contained model change, it does a more intelligent pick-and-choose type diff. may eventually be the default if it doesnt break everything in musio when turned on.