Over 100 Results Functionality

Hey Greg,

Found this handy little gem and wanted to help improve it a bit and add functionality. The code here adds functionality (with testing) for over 100 results, and changes small parts of the original code to be a bit more readable and use some ruby expressiveness. All craiglists results have a footprint for over 100 results, so I simply put a new method for building that uri.

Let me know what you think, I'll be happy to change anything if you don't like it.