This fix aligns with the Android implementation of no delay.

This fix removes all keyboard delay, including the 0.01 second
delay for hiding. I believe this delay existed due to a slight
flicker observed when setting delay to 0. However, by
wrapping the height javascript logic in
`requestAnimationFrame()` the flicker is no longer present.

I believe this is a better solution than ionic-team#2230 because it
avoids adding animations. (Users can do this themselves
by disabling resizing and hooking into keyboardWillShow,
didShow, willHide, and didHide events in javascript.)

It also avoids magic/arbitrary delay amounts, like 0.01.