move to the next slide when clicking - closes #141

Hello,

I like this, but this change introduces a bug. Showoff supports executable code blocks which, when clicked, will run the code and output the result. This change, as it is, produces strange results with those blocks: an overlay is displayed with the execution result, but the slide has changed as well.

I can think of 2 ways of implementing this:

As it is, but forcing all element click events to stopPropagation() if it was not supposed to change the slide (our click events and all user generated click events, which sucks);
Create a method which will only advance the slide if no click handler was triggered until then. If the user wants to advance the slide, he must additionally call our API function to achieve that.

I like the second approach better. It's more "presentation software" style, and involves no additional effort from showoff users.

What do you think? @schacon, want to weigh in on this?

schacon / showoff

move to the next slide when clicking - closes #141 #168