Issue 175 test group deletion new workflow

This is done! Please review and let me know if there needs to be any changes.
I would suggest we do two things:
* update the selector to  `_group_header_locator = (By.CSS_SELECTOR, '#group-show h1')`
* file a bug asking the developers to add a more succinct selector, perhaps `id=group_title` or `id=group_name`. Once the selector is updated we can refactor our test code.

You'll need to update the method that uses the selector. See [0](https://github.com/mozilla/Socorro-Tests/blob/master/pages/super_search_page.py#L19) and [1](https://github.com/mozilla/Socorro-Tests/blob/master/pages/super_search_page.py#L59) for examples