{ok, ...} | {error, ...} interface for describe_volumes
create_snapshot {ok, ...} | {error, ...}
{ok, ...} | {error, ...} interface to describe instances
api change {ok, ...} | {error, ...} signature to ec2 api
Merge branch 'master' of https://github.com/gleber/erlcloud
Merge pull request #48 from fogfish/master

{ok, ...} | {error, ...} signature to ec2 api