Improvements
- Add snap easing config, close issue #407.
- Add 'autoBlur' option, it will auto blur the active Element before scroll start.
BugFix
- Fix a bug that when the 'pullingUp' event triggered and immediately call 'finishPullUp' method will cause 'pullingUp' event never triggered again.
- Fix a bug that button 'click' event will triggered twice if set click option to true.