Added attribute callbacks and event $emittion after sorting completes.

Adds support for deep descendants (thanks @yenoh2 resolves #494) and nesting the repeated items within transcluded directives.

Increase dependencies to jQuery v3.1 & jQuery-UI v1.12

limit jquery version to pre v3

fix bad release manoeuvre

Provide the item.sortable object inside the helper callback.

A great thanks to @iamchairs, @tepez and @michaschwab for their contributions!