Change default behavior of keys:add to upload as key_comment if available.

This edit will default to uploading the users key as identified by its key comment if the key comment is defined, and gracefully fall back to the older method if it is not.

This should improve usability for some users working from multiple workstations.
PEP8 Formatting
Update deis.py
Default login/register URL to http:// schema if it's not specified.
Moved "Terms" section back to top level nav in docs.
Merge pull request #300 from opdemand/299-no-schema-supplied

Fixed #299 -- default login/register URL to http:// schema if it's not specified.
Merge pull request #301 from opdemand/296-terms-sphinx-nav

Fixed #296 -- moved "Terms" section back to top level nav in docs.
Don't prompt users to create an app if runtime=0
Merge pull request #302 from opdemand/250-nodes-scale-msg

Fixed #250 - don't prompt users to create an app if runtime=0
added some error checking for digital ocean
use region_id, not location_id
Refactored provider creds discovery to be more DRY, added alternate AWS vars.
Merge pull request #308 from bacongobbler/306-snapshot-error-checking

LGTM
Merge pull request #309 from opdemand/276-providers-discover-refactor

Fixed #276, #293 -- refactored provider creds discovery
If CM's purge_node() fails then raise an error.
Merge pull request #310 from tombh/purge-node-feedback

If CM's purge_node() fails then raise an error.
Merge branch '232-vagrant-provider-full' of https://github.com/tombh/deis into tombh-232-vagrant-provider-full
Updated docs and only test for avahi-daemon on Linux.
Merge branch 'patch-2' of https://github.com/scottstamp/deis into scottstamp-patch-2
Updated Berksfile for latest deis-cookbook SHA.