use s3 client directly

[arschles]

after #72, use minio-go or the official AWS Go SDK instead of calling to the mc binary directly. this will also remove the need to set the DOCKERIMAGE=1 env var in the docker image

[bacongobbler]

I've been making leaps and bounds with getting boto3 working with minio. Would https://github.com/aws/aws-sdk-go be a potential viable alternative? It could initially be a pain, but migration from minio -> S3 -> riakcs would be a lot easier, I'd imagine

We can talk about this in Boulder next week if it interests you :)

[arschles]

@bacongobbler yes, absolutely that is a viable alternative, and I've added it as an option in the description. I believe that we should support v2, v3 and v4 signatures so we can support older object stores, or stores like GCS that only offer v2 signatures at this time.

And yea, this interests me, so let's talk in Boulder.

[arschles]

note for later, minio-go supports v2 and v4 signature versions, which means that it can support Riak CS