docker: detect defaultNetworkMtu from default route

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: google)
networkdriver: add ErrNoDefaultRoute

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: google)
docker/config: update -mtu flag default

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: google)
docs/cli: add mtu option

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: google)
Do not call Put twice and do not call it on defer

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Fix unmounts out of container export funcs
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Update mkimage-arch.sh

mktemp creates a root directory ("/") with permissions set to 700. Default should be 755 so other users in the container can access its subdirs (e.g http user for nginx for /srv/http/test/index.html).

Docker-DCO-1.1-Signed-off-by: Samuel Andaya <samuel@andaya.net> (github: sandaya)
i was reading, and it sprang out at me :)

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
docs: Installation on Mac OS X 10.6 Snow Leopard
Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)
Merge branch 'master' of https://github.com/ostezer/docker