Fix unset PRELUDE_INTO bug.

A -n test behaves differently with and without quotes.  This fixes
https://github.com/bbatsov/prelude/issues/577
Merge pull request #597 from benprew/patch-1

Update installer.sh
pomodoro, tempbuf and visible bell updates
Merge remote-tracking branch 'bbatsov/master'

* bbatsov/master:
  Fix unset PRELUDE_INTO bug.