README updates - clarifying installation and setup
README updates - clarifying installation and setup

Most people aren't manually installing or running docker images, so that
section of install probably shouldn't go first: reading through the
README for the first time I'd expect new users to get more benefit from
first seeing the section their likely to need.

I also added a new "Setup" section about getting started using the tool
wtih a new project.

codeclimate/codeclimate,codeclimate/codeclimate,codeclimate/codeclimate