work with latest (1.4) golang
show how to get passwordless ssh into the vagrant VMs
don't enter src MACs of forwarded packets in our cache
There is no point, and it populates the cache with entries we don't
need. Local containers will still need to issue an ARP request when
they first talk to an IP corresponding to the MAC, so we learn about
the MAC at that point, just as normally happens.
document mac_cache max age constraint
don't be so defensive
(we are not that paranoid elsewhere)
link to crypto docs from security feature
Merge master into gh-pages