*: Use /usr/bin/env in shebangs for bash & zsh

To increase the portability (OSX for example has zsh under `/bin/zsh`).

meta/git/hooks/commit-msg

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # A hook script to check the commit log message.
 # Called by "git commit" with one argument, the name of the file that has the

meta/submodules

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 [[ $# -eq 1 ]] || { echo "Specify what to do" >&2; exit 1; }