Fix installation docs to use the new boot2docker command: ip

Docker-DCO-1.1-Signed-off-by: Lajos Papp <lajos.papp@sequenceiq.com> (github: lalyos)
Fix typo in networking.md

Minor typo fix
Merge pull request #6566 from jokajak/patch-1

Fix typo in networking.md
Merge pull request #6540 from lalyos/docs-installation-mac-windows

Fix installation docs to use the new boot2docker command: ip