bug fix: touch start events on iOS devices works

It looks like the 'ontouchstart' and 'touchend' events were interfering with each other. I fixed that, but I've only tested on iOS 8. It seems to work just fine with 'click' benighted only event, but older devices might not register it that way? Or maybe older versions on Angular don't map the two together? 

One this to note is that on iOS 8, tapping off the element does not close the dropdown. Not really sure why, though. I didn't want to make too many changes without looking further into cross-device support for touch/click events. 

I also added 'user-select:none' to the stylesheet to prevent the user from selecting the dropdown text when they are tapping on it.