Explicitely add alertmanager to example config (#3383)
Explicitely add alertmanager to example config (#3383)

As alertmanager needs to be configured in the config file in Prometheus 2, I think it is useful to have it in the example config.

Also renamed the rules in the example config so they are explicitely yml files.
kangwoo/prometheus,amorken/prometheus,amorken/prometheus,prometheus/prometheus,Gouthamve/prometheus,keegancsmith/prometheus,Stackdriver/stackdriver-prometheus,GoogleCloudPlatform/prometheus,brancz/prometheus,kangwoo/prometheus,AlekSi/prometheus,amorken/prometheus,prometheus/prometheus,Conorbro/prometheus,kangwoo/prometheus,brancz/prometheus,keegancsmith/prometheus,prometheus/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,Gouthamve/prometheus,prometheus/prometheus,AlekSi/prometheus,GoogleCloudPlatform/prometheus,brancz/prometheus,Stackdriver/stackdriver-prometheus,alileza/prometheus,Conorbro/prometheus,keegancsmith/prometheus,Stackdriver/stackdriver-prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,amorken/prometheus,alileza/prometheus,Gouthamve/prometheus,kangwoo/prometheus,Gouthamve/prometheus,Conorbro/prometheus,Conorbro/prometheus,Stackdriver/stackdriver-prometheus,alileza/prometheus,AlekSi/prometheus,alileza/prometheus,AlekSi/prometheus,keegancsmith/prometheus,brancz/prometheus,GoogleCloudPlatform/prometheus