Add tag to specify minio version to use for documentation build.
The new minio major release broke the build.  We'll need to figure that out but for now use the last major version, which is known to work.
<title>Introduction</title>
<!-- Create S3 server first to allow it time to boot before being used -->
- <host-add if="'{[s3-local]}' eq 'y'" id="{[host-s3-id]}" name="{[host-s3]}" user="root" image="minio/minio" os="{[os-type]}" option="-v {[fake-cert-path]}/s3-server.crt:/root/.minio/certs/public.crt:ro -v {[fake-cert-path]}/s3-server.key:/root/.minio/certs/private.key:ro -e MINIO_REGION={[s3-region]} -e MINIO_DOMAIN={[s3-endpoint]} -e MINIO_BROWSER=off -e MINIO_ACCESS_KEY={[s3-key]} -e MINIO_SECRET_KEY={[s3-key-secret]}" param="server /data --address :443 --compat" update-hosts="n"/>
+ <host-add if="'{[s3-local]}' eq 'y'" id="{[host-s3-id]}" name="{[host-s3]}" user="root" image="minio/minio:RELEASE.2019-06-04T01-15-58Z" os="{[os-type]}" option="-v {[fake-cert-path]}/s3-server.crt:/root/.minio/certs/public.crt:ro -v {[fake-cert-path]}/s3-server.key:/root/.minio/certs/private.key:ro -e MINIO_REGION={[s3-region]} -e MINIO_DOMAIN={[s3-endpoint]} -e MINIO_BROWSER=off -e MINIO_ACCESS_KEY={[s3-key]} -e MINIO_SECRET_KEY={[s3-key-secret]}" param="server /data --address :443 --compat" update-hosts="n"/>
<p>This user guide is intended to be followed sequentially from beginning to end &amp;mdash; each section depends on the last. For example, the <link section="/backup">Backup</link> section relies on setup that is performed in the <link section="/quickstart">Quick Start</link> section. Once <backrest/> is up and running then skipping around is possible but following the user guide in order is recommended the first time through.</p>
