Updates beets to version 1.3.16, which comes with new plugins
"embyupdate", "edit" and "mbsubmit". See the following URL for a
detailed upstream changelog:
http://beets.readthedocs.org/en/v1.3.16/changelog.html
The "mbsubmit" plugin isn't listed there and made it more or less
silently into the release, see beetbox/beets#1779 for the final work on
the plugin.
Tested this locally with a few queries and using the new "edit" plugin.
ac9cea30fb