[slim] Clean up .gemspec
[slim] Failing Feature: slides.slim
[slim] Start using slim 2.0
[slim] Switch to tilt for haml. Support slim.
[slim, haml] Swap out template processors for Tilt
[haml -> generic file] Slight variable rename
[CHANGELOG] We now support Slim
Support the Slim templating language.

You can now choose between Haml and Slim. Make the choice by creating
either slides.slim or slides.haml.