readme: add link to GoDoc in prose

Upon further examination, the GoDoc is a very good source of documentation for this package. Send users there for now. Signed-off-by: Stephen J Day <stephen.day@docker.com>

badge: add nice badges for good health

A good open source project is measured by the number of badges at the top of the README. For now, we have two, but you have to start somewhere. Signed-off-by: Stephen J Day <stephen.day@docker.com>

Modified defaultRWTimeout to 30

Signed-off-by: French Ben <frenchben@docker.com>

Fix copyright statement

Removes placeholder, and adds basic copyright/license section to the README Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Signed-off-by: Stephen J Day <stephen.day@docker.com>

Always negotiate a compatible protocol version

Previously, if the client suggested a newer version then we gave up. Now, we offer to drop back to 9P2000. Signed-off-by: Thomas Leonard <thomas.leonard@docker.com>

transport: remove obnoxious log message

Error was: error handling connection error negotiating version:%!(EXTRA *errors.errorString=bad version negotiation) will close Signed-off-by: Thomas Leonard <thomas.leonard@docker.com>

Signed-off-by: Stephen J Day <stephen.day@docker.com>

p9p: add a marshaller and unmarshaller for `[]Dir`