Sync master (#791)

* Anchor silence regex rules

When user creates a new silence with regex match it's left to the user to anchor it, which is not consistent with Prometheus regex handling (promql/functions.go#L818).

* Serialize AlertStatus as 'status'

AlertStatus doesn't have json tag with the field name, so it's serialized into 'Status', and it's the only uppercase field in the alert object. Tag it with 'status' name for consistency

* Fix lock usage in the types package

Locking is a bit tricky there since some state-modifying methods will call to other methods that also modify marker state, simple defer won't work.

* Throw error when continue in route root of Alertmanager config

* Fix alert status handling in UI

* Fixes #746

Found that we are only defining MarshalJSON for the Regexp type for
references not for the direct object

Also took the time to simplify the json.Unmarshal usage in cli/config.go

* Added unit test for continue in root route error (#768)

* Added unit test for continue in root route error

* replaced %v with %q

* Fix broken link to silence from alert

* Fix broken link to silence from alert

* *: cut v0.6.2 (#777)

* Show startsAt time for pending silences (#778)

* docs: Add note to not load balance Alert trafic

README.md

@@ -201,9 +201,11 @@ Start your prometheus like this, for example:
 
 > Note: make sure to have a valid `prometheus.yml` in your current directory
 
+> Important: Do not load balance traffic between Prometheus and its Alertmanagers, but instead point Prometheus to a list of all Alertmanagers. The Alertmanager implementation expects all alerts to be sent to all Alertmanagers to ensure high availability.
+
 ## Contributing to the Front-End
 
-Refer to [ui/app/CONTRIBUTING.md](https://github.com/prometheus/alertmanager/blob/master/ui/app/CONTRIBUTING.md).
+Refer to [ui/app/CONTRIBUTING.md](ui/app/CONTRIBUTING.md).
 
 ## Architecture