Acceptance testing

[skipor]

Need to automate compile and run of Pandora binary and check its behaviour. It would be great to check it before every PR in CI.
Propose:
Create acceptance_tests directory and create onsi/gomega/gexec driven tests for

• CLI behaviour
• Main plugins behaviour

I imagine tests like

• Before suite: compile binary via onsi/gomega/gexec
• Some test
  • launch httptest.Server and run binary against testdata/http.yaml config
  • Check pandora log output (for data races end errors, for example) and return code.
• Other tests

[skipor]

Well, there are some Acceptance tests already. I think that it is enough at that moment because they are costs too much.