Change to scala-stream-collector: support for IAM roles.

Add a new config option for aws.access-key and aws.secret-key.
If set to 'iam', use scalaz CredentialsProvider.InstanceProfile
to set up API credentials.
Merge branch 'iam-credentials' of github.com:pkallos/snowplow into pkallos-iam-credentials
Merge branch 'pkallos-iam-credentials' into kinesis-1
Merge branch 'pkallos-kinesis-describe-stream' into kinesis-1
Merge branch 'pkallos-future-scala-collector' into kinesis-1