load_credentials_from_metadata
fetch creds from IAM metadata if missing or expiring / expired
use timex
test iam key retrieval
handle expiring / expired keys, test getting keys from IAM
update readme to mention getting keys from IAM roles
Bumping version to 0.1.2.
Adding line to CHANGELOG: * retrieve access keys from IAM roles when running in EC2
Merge branch 'feature/metadata-credentials'