[Tests] Coverage is still low

[vitorfhc]

Output for go test -coverprofile cover.out ./... && go tool cover -func ./c.out:

?       github.com/vitorfhc/bob [no test files]
?       github.com/vitorfhc/bob/cmd     [no test files]
?       github.com/vitorfhc/bob/pkg/bob [no test files]
ok      github.com/vitorfhc/bob/pkg/docker      0.416s  coverage: 19.4% of statements
?       github.com/vitorfhc/bob/pkg/docker/outputs      [no test files]
ok      github.com/vitorfhc/bob/pkg/helpers/fs  0.512s  coverage: 69.2% of statements
github.com/vitorfhc/bob/pkg/docker/client.go:10:        init                    75.0%
github.com/vitorfhc/bob/pkg/docker/image.go:33:         FullName                40.0%
github.com/vitorfhc/bob/pkg/docker/image.go:44:         Build                   0.0%
github.com/vitorfhc/bob/pkg/docker/image.go:83:         Push                    11.8%
github.com/vitorfhc/bob/pkg/docker/image.go:113:        generateFullNames       66.7%
github.com/vitorfhc/bob/pkg/docker/image.go:125:        initLogger              0.0%
github.com/vitorfhc/bob/pkg/docker/image.go:133:        log                     0.0%
github.com/vitorfhc/bob/pkg/docker/image.go:138:        scanBody                0.0%
github.com/vitorfhc/bob/pkg/docker/image_list.go:14:    NewImageListFromYaml    37.5%
github.com/vitorfhc/bob/pkg/helpers/fs/fs.go:10:        FileExists              100.0%
github.com/vitorfhc/bob/pkg/helpers/fs/fs.go:18:        FindFileWithExtensions  100.0%
github.com/vitorfhc/bob/pkg/helpers/fs/fs.go:33:        ReadYamlFile            0.0%
total:                                                  (statements)            27.4%

Total coverage is still low, we need to improve this. Docker functions such as Build and Push may be tested using gruntwork-io/terratest.