Merge pull request #31 from robparrott/master

Refactor data dirs and CLI code a bit;
allow deployment file YAML to specify the NEPHO_INSTANCE_ROLE env variable in the build script, in order to differentiate service tiers.
Merge branch 'master' of github.com:huit/nepho
pass in S3 creds as env variable, and document env vars.
Call bootstrap.sh if available
Merge branch 'master' of github.com:huit/nepho into mediawiki-poc

Conflicts:
	nepho/data/deployments/mediawiki.yaml