Add prerequisites block to readme

[dnskvlnk]

Docker fails to create an image if docker-compose is version 1. This patch explicitly states that it should be v2 or newer

[Stolb27]

@dnskvlnk, can you some additional details to run behave tests?

1. Set IMAGE variable
2. Generate ssh keys that will be used across docker containers

[dnskvlnk]

@dnskvlnk, can you some additional details to run behave tests?

1. Set IMAGE variable
2. Generate ssh keys that will be used across docker containers

I can't confirm presence of an ssh keys related problem

[dnskvlnk]

1. Add allure report
2. Check gpexpand test