Improve test coverage

[dgil]

The test we have now only test a few simple cases. We should improve test coverage.

Also, we could add in the main page a badge with the coverage.

[dkapanidis]

Let's split this to two different scopes. Add CI integration to captain and improve test coverage.

The CI integration is now on #50 issue.

[dgil]

Great!

[dkapanidis]

Created an issue for adding coveralls integration #53