Jetpack: Carousel: A few changes in here: props cfinke
* Clean up the swipe detection: allow vertical scrolling when we're overriding the horizontal touch event.
* When a swipe starts on the next or previous buttons, detect it.
* This is necessary due to the previous commit that enable the display of the next/prev buttons on certain size mobile screens.
* Fixing caption, description, and metadata display on small screens.
* We're no longer "detecting" mobile devices via the user-agent. Most of what we used that for is now being accomplished via the sub-760px media query.
* The image description is moved below the title on small screens, where it feels more natural. On large screens, it's still displayed directly below the image.
* We're now showing the edges of the next/prev images on mobile screens *if* they're big enough. Below a certain size, we are still hiding them.


git-svn-id: https://plugins.svn.wordpress.org/jetpack/trunk@795859 b8457f37-d9ea-0310-8a92-e5e31aec5664