Add custome pseudo element test: child selector after pseudo style is not applied to tag.

i.e.
div::x-thumb > span  style does not apply <div><span></span></div>.
above then the specified x-thumb pseudo in the tag.
Merge pull request #212 from kumatronik/submissions/kumatronik4

Add custome pseudo element test: child selector after pseudo style is no is applied to tag.