Check that service token works with all major methods

[prawn-cake]

WHY VK claims that starting from May 2018, service token is required for all the methods, which means that user / password authentication should be deprecated and service token auth method should be preferred.

WHAT

• Take list of methods and call it with a service token, probably it's a good idea to write a integration test for that
• Clean up old tests, since some of those are failing

[prawn-cake]

which means that user / password authentication should be deprecated and service token auth method should be preferred.

This is not really true. Some of the methods require user token (username + password) and some of them only service token. So no need big updates here