B test197

three commits made on June 6th (today).

There are some unclear points, and they are:
1. changes of webdriver commands (such as open, type, and wait_for_page_to_load) since they seem not to be available for self.selenium...
2. addition of a function in login_page.py. This is because of ensuring that the current log-in user has written the reply.
3. use of xpath for some locators. Due to my limited knowledge about css-selectors..;<

Please feel free to give me suggestions for big changes!