Added stackbrew section in README.md
Added 0.6.0 to registry definition file. Updated latest to include security fix
Freeze required docker-py version to 0.2.1
Refactoring
* Summary class now has its own module
* Added SummaryItem class (Summary HAS-MANY SummaryItem) - more info, easier for persistence
* Logger can now be provided as argument to build_library
* pep8