Add key-repeat feature to next-icon

[artasparks]

The idea is that if you touch and hold on mobile, it should play through several variations.

This request is partly due to fact you can't disable zoom at a div-level

See: http://stackoverflow.com/questions/13886763/disable-zoom-on-a-div-but-allow-zoom-on-the-page-an-alternate-div

To ameliorate the problem, we could add

for iOS to pages where Glift lives. But this isn't at the Glift level.

[artasparks]

Note: with zoom-on-click being fixed, this isn't as high a priority.