Fix build problems on case-sensitive filesystems

Fixes #11.

This is a two-step fix. Step 1 renames all the `appServer` folders to `app_server`, and step 2 renames the `app_server` folders to `appserver`.

I've successfully tested both `git rebase` and `git merge` to update the master branch with this fix, both on case-sensitive and case-insensitive filesystems, so it *shouldn't* cause problems.