.bash_profile: Redirect all `which brew` output
.bash_profile: Redirect all `which brew` output

On RHEL6, `which brew` prints `/usr/bin/which: no brew in …` to stderr. Changing `> /dev/null` to `&>/dev/null` redirects both stdout and stderr to `/dev/null`, silencing the check completely.

Closes #650.

ifdattic/dotfiles