Added tests for pages via Mink

This tests the whole library and pages without mocking via Mink and the Selenium Driver.
Just now only basic but we can improve them and add more later.
I wonder how you're using automated refactoring `Shift+F6` to rename classes in a way that results in filename changes, but class name not. I bet you just rename the file. In that case you need to rename class and PhpStorm will rename file automatically to match.