Support number-pad and other keyboard types

[bolinfest]

Currently, this check is hardcoded for the numeric keyboard type:

      if (screenY === height || this.props.keyboardType !== 'numeric') {
        bottom = -81;
      } else {
        bottom = endCoordinates.height - 40;
      }

But this does not do the right thing for keyboard types such as number-pad:

https://facebook.github.io/react-native/docs/textinput.html#keyboardtype

(Admittedly, the difference between the two is slight. It seems the only difference is the lack of a decimal point in number-pad mode.)