strtolower for Element::name() to fix uppercase element names in some Browsers

The fix suggested in
https://github.com/sebastianbergmann/phpunit-selenium/pull/201

Some browsers like Safari and Opera return uppercase element names for Element::name(). The current behavior crashes on SELECT-tags and even crashes the test Selenium2TestCaseTest::testElementsKnowTheirTagName() because the returned name will be 'DIV' and not 'div'.