Add unit tests.
Move tests to shared drive.

It makes sense for the unit test files to be accessible to the host machine. Since /srv/www is the main location for shared files, move the unit tests co to that folder. Update references to the folder as well.
Remove WP_TESTS_DIR variable.

This just not working, so remove it.
Add comments
Properly handle unit tests on reload.

Check for the correct folder to determine if unit tests are installed. If they are installed, perform svn up instead of displaying "already installed" message.
Setup unit tests from the "trunk" WordPress install.

It is best to do unit testing against trunk. Ideally, I wanted to be able to flexibly test against trunk or latest stable. This is going to take some tinkering to get right, so, for now, unit tests will be run against the trunk install.
Merge pull request #52 from tollmanz/add-unit-testing-wp-cli-round-2

Add WordPress Core unit testing