Fix $.labels -> $labels in blog post (#834)

content/blog/2017-06-21-prometheus-20-alpha3-new-rule-format.md

@@ -64,7 +64,7 @@ groups:
     labels:
       severity: critical
     annotations:
-      description: "stuff's happening with {{ $.labels.service }}"      
+      description: "stuff's happening with {{ $labels.service }}"      
 ```
  
 The rules in each group are executed sequentially and you can have an evaluation interval per group.
@@ -73,4 +73,4 @@ As this change is breaking, we are going to release it with the 2.0 release and
 The converted files have the `.yml` suffix appended and the `rule_files` clause in your Prometheus configuration has to be adapted.
  
  
-Help us moving towards the Prometheus 2.0 stable release by testing this new alpha version! You can report bugs on our [issue tracker](https://github.com/prometheus/prometheus/issues) and provide general feedback via our [community channels](https://prometheus.io/community/).
\ No newline at end of file
+Help us moving towards the Prometheus 2.0 stable release by testing this new alpha version! You can report bugs on our [issue tracker](https://github.com/prometheus/prometheus/issues) and provide general feedback via our [community channels](https://prometheus.io/community/).