shadow-dom: Added tests that checks invalid pseudo element value

Added tests of invalid pseudo element values.
This tests is related to the 'Custom Pseudo-Elements' sections of the specs.
http://www.w3.org/TR/shadow-dom/#custom-pseudo-elements
shadow-dom: Fixed the styles of 'for' loop
Merge pull request #157 from summerwind/submission/summerwind

shadow-dom: Added tests that checks invalid pseudo element value