Rely upon /usr/bin/env to find bash

This allows you to use the homebrew install Bash 4 on MacOS systems. It
should compatible with most if not all modern Linux distros.

nextnumber

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # TODO: Find a less trashy way to get the next available error code
 if ! shopt -s globstar
 then