Changed autoloader handling, minor tweaks to unstick Travis.

With this change bootstrapping the project for testing only requires `composer install` to be run. This will setup Composer's autoloader (`vendor/autoload.php`) in such a way that Ferrit will be able to run tests.

 * Removed the Git submodule
 * Added additional files to .gitignore (`vendor/` and `build/`)
 * Skip the `MIMEDetector` test if `MIME_Type` is not available
 * Instruct Travis to run Composer
 * Instruct Travis to test PHP 5.3.3 in addition to PHP 5.3 (latest stable)

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One of the big things I'd like to move toward is **away** from `MIME_Type` entirely. I think a combination of some other projects would help us get away from this dependency.

This is going to require a lot of work with Composer. How comfortable are you with this projecting having external dependencies managed via Composer instead of Git submodules?

Let me know your thoughts on that direction. :)

Thanks!