Support IE9.

[yoshi6jp]

bug fixed #34.

tested IE9 on windows 7.

selectstart event is fired after mousedown event in IE9. Therefore fixed dragEl condition.
dragDrop method is synchronous. therefore fixed after dragDrop method.

[RubaXa]

Thank U. Over the weekend, I try to review your PR.

[Pickra]

Great job @yoshi6jp 👍
It's working for me and I really needed this fix!
The only comment I would make is:
at line 85 of ng-sortable

you might want to:

if (removed) { items.splice(newIndex, 0, removed); }

Which will help when you want to have this kind of functionality. Which gets messed up when removed === undefined.

[RubaXa]

Has not been able to check PR, my VirtualBox does not work.

[RubaXa]

I cannot approve this PR, because it simply does not work:

• http://recordit.co/0mH6UJ5b2S
• http://recordit.co/ezSkxKI1D9

I think there is not need native implementation, it is enough to use the touch-fallback.

[RubaXa]

Create a branch with support for IE9, through touch-fallback, need testing ;]
https://github.com/RubaXa/Sortable/tree/old-browser

[yoshi6jp]

I tested IE9 on Win7. (branch: old-browser)
I think that _off mousemove event is necessary.

[RubaXa]

Done.

[RubaXa]

https://github.com/RubaXa/Sortable/tree/dev/#features