Add setup and tear down logic

[polina-popova]

Closes #53

[polina-popova]

rocketchat-tests: добавить методы setup и tear_down

[ya7on]

After tear down in terminal is written some tracebacks

02/14/2019 11:29:29 AM Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f85fad14ac8>: Failed to establish a new connection: [Errno 111] Connection refused')': /session/***
02/14/2019 11:29:29 AM Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f85fad14cf8>: Failed to establish a new connection: [Errno 111] Connection refused')': /session/***
02/14/2019 11:29:29 AM Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f85fad14860>: Failed to establish a new connection: [Errno 111] Connection refused')': /session/***

[ABSLord]

Need to remove create_test_user=False from vote_or_die_script_tests.py:
test_cases = VoteOrDieScriptTestCase(options.host, options.username, options.password, create_test_user=False)

[ya7on]

You need to catch exception when RocketChat API is not logged in

[eugulixes]

• There is a typo in enviroment.
• Let's rewrite the docstring: Cleans up the testing environment