Fix global options (gon.options) access

I wanted to decrease graphs height (to fit them to screen):

```diff
diff --git a/pulse.ru b/pulse.ru
index 84d2048..a8f6c4c 100644
--- a/pulse.ru
+++ b/pulse.ru
@@ -5,6 +5,7 @@ PulseMeter.redis = Redis.new
 
 pulse = PulseMeter::Visualizer.draw do |l|
   l.embedded true
+  l.gchart_options height: 250
 
   l.page "All" do |p|
     p.line "Sidekiq queues" do |w|
```

No effect!

I debugged.