Add link to godoc in the README
Add link to godoc in the README

As the documentation in this library is in pretty good shape, it's
worthwhile adding a link here to GoDoc.

Signed-off-by: Dave Tucker <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@socketplane.io>

paravmellanox/netlink,mcastelino/netlink,chantra/netlink,porjo/netlink,axsh/netlink,ninjadq/netlink,mrjana/netlink,bboreham/netlink,vishvananda/netlink,clearlinux/netlink,nickethier/netlink