should fix #618 and #597

oldIndex was changed first by with the item being dragged, but also by the drag event of the parent (which should be avoided when we are not using the drag-handle)

This event will fire when an element is chosen, and is particularly
useful for providing the user with a visual, auditory or tactile indication,
in case a delay was enabled.

And so on: #558, #547, #542, #537, #532, #516, #500, #489, #489, #447, #475, #459, ##422, #411, #356

when nesting Sortable's, we're not interested in this error:
"HierarchyRequestError: Failed to execute 'appendChild' on 'Node': The new child element contains the parent."

As done in the other place where `dataTransfer` is used.
This is to support fake html5 drag and drop events, where `dataTransfer` is not accessible. Use case: Selenium testing with ePages-de/chromedriver-html5-dragdrop

#356 Fixing issue where dropping an item on the right end of a horizontally layed out drop zone does not add the item

fix http://jsbin.com/cuduyo/edit?html,css,output

compatible with 
flex-direction: row
flex-direction: row-reverse
https://developer.mozilla.org/fr/docs/Web/CSS/flex-direction

_emulateDragOver optimized to reduce the interval tics. 
That provides a fluidity similar to the native drag and drop mode.

see #422

drag/drop handlers should be disabled in fallback mode to avoid unwanted behaviors

removed the default behaviour to append the cloned Element to the body.
now the cloned Element gets added in the same parent, with the addition
of the class defined in options.fallbackClass.
added the possibility to change the fallback class.
added the possibility to decide wheter the fallback should be cloned
into the same parent or to the document's body.

wasn't merging all necessary stuff. now it should be fully functional

modified the private _onMove prototype, so it calls events on it's
source Element like it's sibling function _dispatchEvent
added the handleMove, which listens to the onMove events to the react
mixin

added forcePolyfill option.
forcePolyfill is made to make cross-browser testing more easy.
forcePolyfill provides a reliable, consistent cross-browser Solution for
Sortable.
forcePolyfill gives us the possibility to change the way "dragged items"
lok like.

Bump minor version number