Code improvements

Added optional 'context' to selector ($$) function
Use selector function where possible to reduce double-code
Optimize event handling code

I made theese optimizations while searching for this bug: https://github.com/nolimits4web/Swiper/issues/318 but still did not manage to find the exact problem. Click event becomes canceled after some actions. Why did you move slide click code outside of onTouchEnd method? Using onTouchEnd() to trigger slide clicks requires less code and less events need to be bound to the DOM.