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
Fix redirection of IO streams
Merge pull request #599 from avsej/fix-io-redirects-in-installer

Fix redirection of IO streams
Merge branch 'master' of github-personal:bbatsov/prelude