phabricator: allow specifying reviewers on phabsend
Sometimes people want to specify reviewer explicitly for a stack. The
webpage only allows changing reviewer for one revision at a time. This patch
adds a `--reviewer` flag to make it easier to specify reviewers.
Test Plan:
On a test Phabricator instance, enable `differential.allow-self-accept`,
assign myself as a reviewer and make sure it works. Also try an invalid
username and make sure it raises.
Differential Revision: https://phab.mercurial-scm.org/D38
#require docutils gettext
$ $TESTDIR/check-gendoc it
checking for parse errors