Verify mojo added to fail the build when errors occur in other Mojos

# Fixes #14 

- Added a Mojo that runs during the verify phase that fails the build if any mojo registered a plugin error prior to it.
- The StartContainer and BuildImage Mojos now register a plugin error when something goes wrong
- The PushMojo will fail the build when a push fails
- Updated the integration tests to use the verify mojo
- Fixed the simple-it Dockerfile, nginx wasn't being installed properly anymore.