Create a servlet (available at `/list`) that lists and links to all the test files.

I've come to appreciate a less automated approach to the unit tests: instead of necessarily running them on the local machine, then telling a browser to visit each page in turn, we can just start the server and manually visit the URLs.

In doing so, we lose the ability to have the command line keep track of passes/fails/errors, but in exchange we get the HUGE win of being able to start the test server on one machine and visit it on another. For IE testing in particular this is much preferred, because it means I don't have to install Ruby and Git on four different modern.ie VMs.

The aim here is to make it easier to visit each test page in turn. This doesn't replace the automation approach; it just adds a new tool to our belt. I've paired it with a new Rake task on the Prototype side that runs the test server indefinitely: it collects/adds the tests, starts the server, but never actually calls `run` on the runner.