Unxfailed test_that_checks_the_tabs() and updated the test logic according to the comments in Bug 824471 - New Personas tab on mobile site not working as expected

Added a new page object for themes page, for now this is used only as a return for clicking on the themes tab
Update after review. Removed init method from themes page object.
Merge pull request #692 from chirarobert/update_test_that_checks_the_tabs

Unxfailed test_that_checks_the_tabs() and updated the test logic accordi...