Update documentation to include SSHKit example page

There's a few other tidy ups in there too. Not sure if all are wanted.

The "debugger" gem isn't compatible with ruby 2.0.0 from what I can see. Why would that be required in this project?

Also, I wasn't sure about the expected process of running jekyll build and having the built files checked in to git too.

Perhaps the addition of a README or a Contirbuting guideline would make this easier for others in future.