Zepto's 'tap' implementation interferes e.g. with Video.js

[emkayy]

Using Zepto touch on the same page as the popular Video.js video player (and most likely other custom touch implementations) cause a double invocation of the handlers bound to 'tap'. This way the play / pause toggle gets 'tapped' twice, resulting in the same state as before the user interaction (keeps playing or stays paused).

[emkayy]

@madrobby May this be related to #1301