add a test to see whether ethtool is available before trying to run it
added Boot2Docker instructions, and simplified the message when ethtool is missing
Mention that we need Go dev tools to build weave
Merge branch 'master' into 14_run_in_boot2docker
Removed small change from README.md
Merge pull request #16 from bboreham/14_run_in_boot2docker

make weave work with boot2docker