tests for chapter '8.1 Extensions to Document Interface'
improving tests according to Dominic's notes
BODY element visibility: must always be displayed no matter what

Signed-off-by: AutomatedTester <dburns@mozilla.com>
Replacing use of find_element_by_tag_name that doesn't exist in the spec

Signed-off-by: AutomatedTester <dburns@mozilla.com>
changing tests to conform with current version of the specification
 tests for WebDriver executeScript

Signed-off-by: AutomatedTester <dburns@mozilla.com>
Merge pull request #989 from sgrekhov/submission/unipro-custom-elements-14

tests for chapter '8.1 Extensions to Document Interface'