Remove all argument handling from tmuxifier-tmux

It's meant to be a wrapper for tmux, allowing additional arguments to be
passed. Hence having the wrapper itself intercept -h as previously, or
--help as removed in this commit prevents the wrapper from working
properly.

libexec/tmuxifier-tmux

@@ -2,16 +2,4 @@
 set -e
 [ -n "$TMUXIFIER_DEBUG" ] && set -x
 
-# Load internal utility functions.
-source "$TMUXIFIER/lib/util.sh"
-
-# Provide tmuxifier help
-if [[ " $@ " == *" --help "* ]]; then
-  echo "usage: tmuxifier tmux [...]
-
-Wrapper command for Tmux executable allowing Tmuxifier to pass in any custom
-arguments specified in the TMUXIFIER_TMUX_OPTS environment variable."
-  exit
-fi
-
 tmux $TMUXIFIER_TMUX_OPTS "$@"