Includes a composer.json file for dependency management through Composer

Hopefully you'll choose to accept this pull request, but this should make dependency management a bit easier for everyone who uses Composer to track their wordpress plugins. For those who don't use Composer, they can simply ignore the file or delete it.

![image](https://f.cloud.github.com/assets/200190/2079296/a860864e-8dc8-11e3-816a-d5fde5269bb4.png)

I've included two requirements for the composer.json file:

1. **PHP 5.3.2**. Feel free to lower or higher the version requirements to fit the adequate version needed for this plugin.

2. **composer/installers** so the plugin installs properly to the wordpress plugins directory when ran with ```Composer Install```.

It may be wise to include wordpress as a requirement as well but I'll leave that up to you.

You may also want to submit your plugin to [Packagist](http://www.packagist.org) so others can enjoy your work and install this via Composer with ease.