Swipe bumper for end of stack

[Watson-B]

This idea was discussed originally in #710, after discussion with @ezl we have a solution to move forward with. For clarity's sake, I am closing that issue to make things clearer.

When the user is at the beginning of the stack, and swipes to go previous, we will show a swipe bumper telling them to go the other way (seen below). The toast will enter from the bottom of the screen, and swipe away when the user swipes to the next card.