Changed logging to use glog library.

Also fixed versioning and added check for test image existence when running integration tests.
What I'd like to see still, is the possibility to redirect docker stderr & stdout to logger, as well as forcing glog to spit everything to stdout and not stderr as it is right now.

@csrwng @bparees comments welcome.
The logging of individual files being tarred/untarred should likely be another level of logging. When debugging builds, a lot of times I wanted to see more of what was going on, but the logging of individual tar/untar files would just clutter everything.