Release documentation improvements resulting from the 0.0.6 practice release

See:
 * Original release process ticket #293  
 * Example download links: https://github.com/ClusterHQ/flocker/issues/488#issuecomment-51506871
 * Release branch: https://github.com/ClusterHQ/flocker/compare/release/flocker-0.0
Above this is called the "flocker development machine" and here it is the "Flocker development environment". These should be consistent.