Modified to initialize variables in _onDrop. so destory function does…

Fix for Issue #580 [Angular] Javascript error when moving items between two lists very fast #683

Sometimes evt.from is different from evt.item.parentNode because the item has been moved already so using evt.item.nextSibling won't work when doing evt.from.insertBefore, because nextSibling is not a child of evt.from.

So in those cases we use evt.clone.nextSibling instead.

fix for sorting elements within a non-homogenus list of elements

The _closest() method already defined a way to do what _matches() was
trying to accomplish.  This pulls the functionality out of _closest() so
that it can be reused outside of _closest() but refactors _closest() to
use this new _matches() method.

For instance, say you are sorting tbody's within a table element.  There
can also exist tfoot and thead within the table element.  The _index()
function assumes that the list of elements within the parent is
homogenus (ie: just li's below an ol/ul).  This isnt the case when
sorting tbody under table.  This is edge case until you want to group
tr's under a table and sort on those groupings.

format comments

add Sortable as dependency for knockout-sortable

fix import polymer readme closes #642

Remove Polymer from bower dependencies

Fix to knockout sorting when dragging item index 1 to 0.

Allow a custom setState handler on the using component

The items would not swap positions when you dragged item with index 1 to
the top of the stack at index 0.

Add Polymer Support

Only components having a state are currently working correctly with the sortable mixing. The proposed fix is to allow custom state handling method to be passed in as config.

Delete log.txt

Should this file be in the repo?

more reliable way to get the DOM Node

with React v0.14 this.refs.*.getDOMNode() is deprecated,
we have to use this.refs.* instead, to reference the DOM Node.

this is a implementation, that is backward compatible

* misspelled ref in README fixed
* fixed Demo of forceFallback

Add `getContainer` option for better react version support