Experimenting with using Travis CI for a Racket project.

Until Travis CI gets built-in support for Racket, we can use the
`before_install` clause of `.travis.yml` to download and run the
Racket installer.

To add this capability to your project, simply add the
[example `.travis.yml`](https://github.com/greghendershott/travis-racket/blob/master/.travis.yml)
to your repo. You may need to change its `script` section's `raco
make` and `raco test` parts.

> **NOTE:** In the `before_install:` step, be sure to pipe the `install-racket.sh` script to `bash` (_not_ to `sh`).

Here's a "badge" showing the status for the `master` branch of this
repo:

[![Build Status](https://travis-ci.org/greghendershott/travis-racket.png?branch=master)](https://travis-ci.org/greghendershott/travis-racket)