Add Activity indicator Mode

[mojtabacazi]

So in this mode, there would be an activity indicator (spinner, custom view, etc) instead of the icon. A progress bar would be helpful as well.

[KrauseFx]

This totally makes sense. I'd prefer to just offer an UIView as parameter instead to be fully flexible. What do you think?

[mRs-]

This would be awesome!

[damien-rivet]

Hi there,

If we push the idea a little further, you can even add a progress bar, with a default color based on the type of the message.

The bar color should also be customizable to allow a greater range of implementations.

Just my .02 ^^

[mRs-]

this should be fixed if we implement #134