Minimum and Maximum Year/Date and Validation

I have made some changes that i need for one project.
- Added minimum and maximum year parameters in init method to allow change the values that was constants.
- Added minimum and maximum date parameters in init method to allow same behaviour as item above and also allow minimum month for minimum year and maximum month for maximum year. It have same behaviour  as UIDatePicker, when user tries to select an invalid month, it scrolls to minimum one.

I have created the .podspec file because i had some problems with the use of ARC and the delegate being a weak parameter.


I hope you like my changes. If you see any problem or changes that I could make, do not hesitate to talk with me.

Thanks!