Added some docblocks for use with phpdoc
Renamed the Iterator class back to ResultInterface

This better represents its purpose
Added type hinting where appropriate/possible
Updated to use the new fetch style
Throw an error if an invalid parameter is passed to the where() method
Deprecated the old convenience methods

These are misleading and inflexible, and recent improvements to the Result/Cache classes mean they are no longer required
Updated the README with some basic documentation