immutableTop option

[dhilt]

For issue #229. Adapter.applyUpdates method got new options argument:

• applyUpdates(index, newItems, options)
• applyUpdates(updater, options)

The options is an object that might contain immutableTop boolean property:

{ immutableTop: true }

The default value is false, which provides backward compatibility.

If the value of immutableTop option is true, left border index of Buffer array will never change during insert/delete operations. For example, removing first item in "1: item 1", "2: item 2", "3: item 3" list will result in "1: item2", "2: item 3" list. Here the template is {{$index}}: {{item}}.

[priandsf]

That was a quick turnaround :-)
The changes you made are actually the exact same ones that I made, except that you used an options object while I used a simple boolean param. But that's fair, the objects gives more options going forward.
I merged your changes into our own private branch and it worked like a charm. Thanks a lot!