Card-reveal with more flexibilities

I was trying to use the card reveal feature. I had a button on my card that does something, and that button always pull up the hidden card everytime I click it because of the way the click event was binded to the card.

I refactored the card-reveal feature based on the original function written by @acburst and make an extended Jquery function. The new `reveal` function gives users more control over the whole card-reveal action now.

Updated the documentation, too!