Feature/location class

Hey, its [stlunatic102 from reddit](http://www.reddit.com/r/iOSProgramming/comments/26iip0/czweatherkit_a_simple_cocoa_weather_library_ive/chrn7bc)! I liked the work that you did and really wanted to see the change that I had mentioned integrated into your lib.

I created a class called `CZWeatherLocation` that is used while creating the request. Each service is responsible for generating the query based on the state of this object right now, but it'd be great to see each service implement a protocol to serialize this object. Might generate some more maintainable code down the line rather than the giant if-else block that does the logic.

Let me know what you think!