changes confirm on kill of window/pane/session

 - don't confirm when killing pane
 - don't confirm when killing window
 - confirm when killing session

The latter is important since shifting from a pane below requires you to
press "ctrl-b k" and killing a session is mapped to "ctrl-b ctrl-k" -
and thus if typing the k before letting go of the ctrl button makes the
complete session dissapear. (And without this change, it happens without
a prompt at all)
dont install browsers through cask

alfred cannot read the symlinks, and their real path are added to
alfred. This means that os x sandbox is not in effect, and 1password
will not work with them then.

Manually install browsers into /Application