Merge pull request GoogleContainerTools#148 from nkubala/v0.5.2

cut version v0.5.2

Merge pull request GoogleContainerTools#138 from nkubala/docs

Add note about referencing images by IDs in readme

Merge pull request GoogleContainerTools#112 from nkubala/release

cut v0.5.0 release

v0.4.1 Release

Merge pull request GoogleContainerTools#81 from aaron-prindle/cobra-args

updated cobra and switched some code to use Args concept

Merge pull request GoogleContainerTools#81 from aaron-prindle/cobra-args

updated cobra and switched some code to use Args concept

Merge pull request GoogleContainerTools#23 from abbytiz/ReadMeKnownEr…

…rUpdate

Adding known issue of etc/docker/certs documentation.