Initial commit

In this first commit, I've moved over the interesting code from the
diffux repo, created a gemspec file, introduced rspec and verified that
specs are running.

In its essence this should be seen as a pure move. I did change a couple
of lines, but that was only to make sure all the dependencies were in
place. There were two references to `Rails` that I had forgotten to
remove in previous cleanup commits in the diffux repo. But I figured
those were small enough to just bake in to this commit.
Namespace public-facing classes

To avoid contaminating the global namespace, I'm wrapping all
public-facing classes in a "Diffux" module.
Change version to 0.0.1

This follows the convention from the RubyGems Guides website.
http://guides.rubygems.org/patterns/