Add guide for OpenFaaS on DigitalOcean (Swarm)
Add guide for OpenFaaS on DigitalOcean (Swarm)

This commit adds a guide to getting started with OpenFaaS running on
DigitalOcean, it includes simple single node swarms up to multi-node
behind a DigitalOcean load balancer.

Signed-off-by: John McCabe <a51dda7c7ff50b61eaea0444371f4a6a9301e501@johnmccabe.net>

alexellis/faas,alexellis/faas,openfaas/faas,alexellis/faas,alexellis/faas,rgee0/faas,openfaas/faas,alexellis/faas,rgee0/faas,rgee0/faas,rgee0/faas,alexellis/faas,rgee0/faas,rgee0/faas,alexellis/faas,rgee0/faas,openfaas/faas,rgee0/faas,rgee0/faas,rgee0/faas,alexellis/faas,alexellis/faas