Fixed Panel Height and Updated Podspec

I've changed the picker's panel height to match all of Apple's demonstrated uses of any sort of modal picker. For example, in the Calendar app, the panel height now matches that of the date picker when you edit an event's start/end time. Additionally, it matches both panel height and toolbar height for Safari's implementation of a modal picker, which can be demonstrated [here](http://www.w3schools.com/tags/tryit.asp?filename=tryhtml_select).

I've also updated the podspec to match CocoaPods's [model podspec](http://docs.cocoapods.org/specification.html).