First pass DigitalOcean instructions.
New whitelisted words.
Finish up DigitalOcean instructions.
Merge remote-tracking branch 'origin/master' into document-digitalocean-FLOC-985

Conflicts:
	docs/gettingstarted/installation.rst
Add DigitalOcean section link
Consistent link to fedora install instructions
Install a digitalocean supported kernel and power cycle
remove unnecessary downgrade instructions
Clearer power up sentence
Standard prompt
Mention the minimum required kernel version
ssh back in and...
Move open ports warning to the generic fedora installation instructions
use an rfc5737 Ip address
Merge pull request #974 from ClusterHQ/document-digitalocean-FLOC-985

flocker-node installation instructions for DigitalOcean 

Author: @itamarst, @wallrj
Reviewers: @tomprince, @itamarst 

Fixes https://clusterhq.atlassian.net/browse/FLOC-985