Update the README.md to point to the correct Discovery documentation.

Signed-off-by: Nick Schuch <nick@myschuch.com>
Merge pull request #196 from nickschuch/master

Update discovery link
log all errors

Signed-off-by: Victor Vieux <vieux@docker.com>
Merge pull request #199 from vieux/log_errors

log all API errors
attach support

Signed-off-by: Victor Vieux <vieux@docker.com>