Changed index argument of action.scrollStart method
Pass new "direction" argument to action.scrollStart() & action.scrollEnd() option methods
Fixed a bug: "this.", "this." element object would be shared between multiple instance
Fixed a bug that "action" object would be shared between multiple instance
Added demo: multiple instance
Merge branch 'gh-pages' of https://github.com/seckie/backbone-slider
Added "next" & "prev" methods to controll slider from instance