Add support for parent elements by handling :parent selectors.
Update github pages to reflect changes in interface.

 * "Search" is no longer a button in the header
 * hrefs updated
Merge branch 'master' into child-elements
Add parent element in search page model to test_github to test child elements.
Get the parent element from the page rather than the session, to fix validation issues.
Add :proc to documentation for +element+.