Remove CURRENT_DIR variable from a helper script

Fixes #200

scripts/helpers/tmux_utils.sh

@@ -1,6 +1,3 @@
-CURRENT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-source "$CURRENT_DIR/plugin_functions.sh"
-
 reload_tmux_environment() {
 	tmux source-file $(_get_user_tmux_conf) >/dev/null 2>&1
 }