scripts: Better shebangs

contrib/imm-o-matic

-#! /usr/bin/python3
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 #
 # Copyright 2015-2016, Roland Mas <lolando@debian.org>

scripts/shopoob

-#!/usr/bin/python2.7
+#!/usr/bin/env python
 # -*- coding: utf-8 -*-
 # vim: ft=python et softtabstop=4 cinoptions=4 shiftwidth=4 ts=4 ai