[Documentation] Link to URL rewriting directives is down

[verax5]

This page:
https://github.com/klein/klein.php

'Getting started' section, in #3 it links user to URL rewriting rules but the gist is down:
https://gist.github.com/874000

[wls]

For others, take a look at https://gist.github.com/RaVbaker/2254618 -- while the documentation link needs fixing, this resource gives a great explanation in the meanwhile.

[funkytaco]

I like this one better https://gist.github.com/jamesvl/910325