Adding RailsBridge Boston 1.2014 ruby workshop mods

We taught the sites/ruby curriculum for our January workshop. It had never been taught before, so we fleshed out the content. 

Modifications include:
* fleshing out all the sites/ruby workshop content -- by  @janetriley, @mxie, and @dpickett 
* Adding the 'challenge' tag to the dsl --  @dpickett

There are still improvements to be made.  I'd like to commit what's here and iterate rather than wait until it's perfect.