Added the support for vertical swipe direction.

[rFlex]

Hey,

I just found out your lib, thanks for the sharing, this is really well done. I had the need for the support of the vertical swipe, so I added a "allowedSwipeDirections" property in the MDCSwipeOptions. By default it is set to MDCSwipeDirectionLeft | MDCSwipeDirectionRight. I had to change the const value of the MDCSwipeDirection in order to use the "OR" operator properly.

[SohailKh]

Hey, just wanted to say thanks!

[clsource]

Hey thanks for your code I was able to add full functionality of swipe Vertical Dectection and Programatically too!

Check it out! :+1: :heart: https://github.com/clsource/MDCSwipeToChoose

[vikmeup]

@rFlex were you able to test it on iPhone 5S, 6, 6 Plus?