Print Consul version on startup

[msabramo]

Along similar lines to hashicorp/vault#765, should Consul also print its version when starting up, to aid in troubleshooting?

Currently it prints info that's very similar to what Vault prints:

CORP\marca@consul03:/opt/consul$ tail -f /var/log/consul
==> Starting raft data migration...
==> Starting Consul agent...

==> Starting Consul agent RPC...
==> Consul agent running!
         Node name: 'consul03.corp.surveymonkey.com'
        Datacenter: 'monkeytest'
            Server: true (bootstrap: false)
       Client Addr: 0.0.0.0 (HTTP: 8500, HTTPS: -1, DNS: 8600, RPC: 8400)
      Cluster Addr: 10.128.40.149 (LAN: 8301, WAN: 8302)
    Gossip encrypt: false, RPC-TLS: false, TLS-Incoming: false
             Atlas: <disabled>

I figure it might as well print the version, just like Vault now does, thanks to @jefferai's fine work on hashicorp/vault#765