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

Assume that el.className === "foo bar"
Assume that your selector is "DIV.foo.bar"

(' ' + el.className + ' ').match(re) will only have one match - " foo " - because the "\\s" trailing character on "foo" prevents " bar " from being matched

EZ fix is just to make sure the trailing whitespace is not consumed by the regex

All modern browsers seem to support `window.pageXOffset` and `window.pageYOffset`, which are aliases for `window.scrollX` and `window.scrollY`.

IE doesn't seem to have `window.scrollX` and `window.scrollY`.

fixes #302