Fix issue #217

New Props

swipeThreshold: Integer, default 30
- A percentage of how far the offset of the current slide is swiped to trigger a slide event.
  e.g. If the current slide is swiped less than 30% to the left or right, it will not trigger a slide event.
stopPropagation: Boolean, default false
- Automatically calls stopPropagation on all 'swipe' events.
preventDefaultTouchmoveEvent: Boolean, default false
- An option to prevent the browser's touchmove event (stops the gallery from scrolling up or down when swiping)