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
2.4.2 Update
slidesPerView "auto" support on fix loop method

On "slidesPerView: auto" (NaN value) the pagination lost the position and the loop is broken. Adding support for "auto" for infinite loop slides
Removing wrong copy-paste

Removing //Fix For Positive Oversliding
hash is defined 2 times
Merge pull request #590 from yukulele/patch-2

hash is defined 2 times
Merge pull request #588 from andreybs11/patch-1

slidesPerView "auto" support on fix loop method
Update to correct dev version
loop and autoplay bugfix
Merge pull request #608 from hiroqn/master

loop and autoplay bugfix
remove plugins from repo
remove previous dist files