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.
My goal is to have currently 4 levels:

* 0 - (default) where you get only the information the image was successfully built
* 1 - where you get just the basic information regarding the build process
* 2 - where you get very detailed information regarding the build process
* 3 - where you get no 2 with all the tar files (per @csrwng request).

But I'm open to any comments on this.