Add domain and subdomain support for MinioAPI

This change brings in domain and subdomain support

   - ./minio --domain "yourminiodomain.com"

This change brings in a much needed feature by keeping
bucketnames as part of your 'DNS' name.

All your existing applications can be migrated off from s3 to
Minio without little to no modifications.

NOTE: Setting up DNS for your `buckets` is out of scope of this feature

pkg/httpserver/httpserver.go

@@ -27,7 +27,7 @@ type HttpServerConfig struct {
 	TLS       bool
 	CertFile  string
 	KeyFile   string
-	Websocket bool
+	Websocket bool // implement it - TODO
 }
 
 type HttpServer struct{}