This simplifies some of our dependencies.
As an example, we really don't want compose.js
to depend on stream_subscribers_ui.js, since
the former doesn't use any actual UI code from
the latter.
We also rename the two functions here:
invite_user_to_stream -> add_user_ids_to_stream
remove_user_from_stream -> remove_user_id_from_stream
(The notion of "inviting" somebody to a stream is
somewhat misleading, since there is really no invitation
mechanism; you just add them.)
Apart from naming changes this is a verbatim code move.
Finally, we eliminate a little bit of test cruft--the
`override` helper already ensures that a function gets
called at least once during a test.
Steve Howell