Added Whitespace Sanitation for Kill Ring
Added Whitespace Sanitation for Kill Ring

Empty strings (whitespaces only) are no longer added to the kill
ring to avoid cluttering the ring. Furthermore, we now strip
the copied string.

sublime-emacs/sublemacspro,seanvk/sublemacspro,grundprinzip/sublemacspro,seanvk/sublemacspro