Improve testing for Slugrunner

[smothiki]

As of now slugrunner is a part of full E2E test. But if we look at functionality here slugrunner only does. two things in DEIS. Takes a slug file extracts and runs the code according to programming language .
Any PR in slugrunner should or also do this test instead of running entire E2E suite.

refer deis/workflow-e2e#303

[Cryptophobia]

This issue was moved to teamhephy/slugrunner#5