createS3Bucket does not strip the s3:// prefix

[jjacobson93]

Assuming AWS_S3_BUCKET_NAME is something like s3://my-bucket, then bucketS3Uri=s3://s3://my-bucket:

    local bucketS3Uri="s3://$AWS_S3_BUCKET_NAME"

(https://github.com/frekele/helicopterizer/blob/master/scripts/core/helper.sh#L198)

This should be:

    local bucketName=$(removeS3Prefix $AWS_S3_BUCKET_NAME)

I will make a PR when I can.