Allow custom render item to wrap touchable component

[avertin]

This library wraps all items that it renders in a TouchableOpacity. This is a problem if you want to use your own custom Touchable component. With the current implementation, the items are be double wrapped in Touchable components so the custom Touchable component never gets press events.

This change adds a new prop called dontWrapItems. If this is set to true, then the library will not wrap the items in a Touchable component and instead expect the renderItem component to handle the wrapping itself. To get everything to wire up, the library will need to pass delayLongPress, onPressOut, and onPressOut to the custom Touchable via a callback in renderItem.

If the maintainer is onboard with this change, I am happy to update the readme with this info as well.

Originally written by @aarondail

Also requested by @sirajalam049 - issue #109