2.3 Update

2.3 Update and new plugins
Removed audio
2.3 JSON
fix not passing correct 'this' to onSwiperCreated callback
Merge pull request #457 from brumm/patch-1

fix not passing correct 'this' to onSwiperCreated callback
Return duration within onSetWrapperTransition callback
New progress effects demos
2.4 Update
2.4.1 Update
Fixes

- improved threshold behavior
- fixed autoplayDisableOnInteraction
- fixed <select> on Android
- new ability to use container as event target
- small fixes
- updated 3D Flow
- ie11 support
Fix for Issue #550

IE throws an error when calling insertBefore when beforeSlide is
undefined, other browsers do not.  I've added in an if/else to handle
the situation when beforeSlide is undefined so that the slide is still
added to the wrapper and prevents a JS error in IE.
Merge remote-tracking branch 'upstream/master'
added is-duplicate class to all duplicate slides

added is-duplicate slides to all the duplicates to that they can be easily picked out in situations where developers need direct access to them.
Merge pull request #551 from Evidica/master

Fix for Issue #550
Update idangerous.swiper.js

changed is-duplicate to `swiper-slide-duplicate` and added a var `slideDuplicateClass`
Update idangerous.swiper.js

changing the addClassToHtmlString to be more generic and not rely on ul.
Merge pull request #553 from GalCohen/master

added is-duplicate class to all duplicate slides
Fixes

Fixed #550
Fixed #417
Fixes

Fixed #561
Fixed #560