Add the ability to pass consul client config via registry options.

This can be used when you need to configure the consul client to use a specific configuration (E.G to pass a Token if consul is using ACL policies)

registry/consul/options.go

@@ -0,0 +1,16 @@
+package consul
+
+import (
+	consul "github.com/hashicorp/consul/api"
+	"github.com/micro/go-micro/registry"
+	"golang.org/x/net/context"
+)
+
+func Config(c *consul.Config) registry.Option {
+	return func(o *registry.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, "consul_config", c)
+	}
+}