Restore optionality of loginWithPassword/changePassword callbacks.

Fixes a regression in 0.8.2.

Fixes #2255.
Update BUNDLE_VERSION note in meteor script
Observe-sequence package recognizes different cursors by checking the interface
of observe and fetch.

Before it checked that the cursor is an instance of Minimongo.Cursor.
Revert change to warning text, going to do this on Monday
install script should write files as current user

If you ran it as root before, it would write files as whatever uid we
had on our buildbot. Oops!

Fixes #2249.
Clarify that your publisher must do SOMETHING

Either return cursor(s), or use the low-level API.

Fixes #2253
merge