Add support for Travis CI and coveralls.io

Just merge this and go to [Travis CI](https://travis-ci.org/) and [coveralls.io](https://coveralls.io/) to set things up for your own repo.

[![Build Status](https://travis-ci.org/msabramo/sh.png)](https://travis-ci.org/msabramo/sh)
[![Coverage Status](https://coveralls.io/repos/msabramo/sh/badge.png?branch=travis)](https://coveralls.io/r/msabramo/sh?branch=travis)

[Sample passing Travis CI job](https://travis-ci.org/msabramo/sh/builds/14027776)
[Sample coveralls.io job](https://coveralls.io/builds/321105)