Added isFirstSlide and isLastSlide functions
check window.ontouchstart != null (required for qtwebkit)
Merge pull request #337 from jjallaire/ontouchstart-nullcheck

check window.ontouchstart != null (required for qtwebkit)
Merge branch 'master' of https://github.com/gouravtiwari/reveal.js
added isFirstSlide/isLastSlide api methods