Don't make unisubs a package

According to the comment this was needed for a django bug, but it
doesn't seem to be needed anymore.  I manually verified that the
/en/jsi18n/ page stays the same after this change (and also that that
page is basially useless).

This allows us to remove a hack from startup.py that was messing with
readthedocs.
Merge pull request #1840 from pculture/remove-unisubs-package

Don't make unisubs a package