bin/ack-wrapper: Handle STDIN being a pipe

* If STDIN is a pipe ("test ! -t 0") use `cat` to redirect stdin to
  stdout and pipe the result to real-ack.
* Switch back to using "command ack" rather than "$(type -P ack").
  `type -P` is bash-centric. Try to be /bin/sh compatible.
* Use clear "${VAR}" syntax around all variables, for consistency.
.vim/colors: Misc clean-up

* colors/neon.vim: Remove empty file. :-\
* colors/murphy.vim: Fix fileformat from DOS to Unix.