Change to composer installed Slim, xdebug fixes, and remove hard coded path

I've changed to use a composer installed Slim rather than the one in the repo, some fixes for xdebug users and removed the hard coded path (which admittedly doesn't conform to the pattern set by FA).

I'm planning on making additional changes as follows:

* pull out the routes into separate files, one per group.
* add more api methods

Let me know if you're wanting PRs to this project.