Adding a keyboardVisible property to the completion block.


Fixes a warning in `UIImage+RZSnapshotHelpers`
Adds a keyboardVisible property to the completion block of the keyboard listener.  

**NOTE** this changes the method signature so I wouldn't recommend pushing this to master until we have more changes that need to go in.
This will break in projects that are not using modules, and it’s converted to modules behind the scenes anyway for projects that are. I would undo this.