readme, more examples

README.md

@@ -7,20 +7,41 @@ default), Graphite, or JSON.
 
 ### Examples
 
+Help:
+
+```shell
+$ sensu-prometheus-collector -h
+Usage of ./sensu-prometheus-collector:
+  -exporter-url string
+        Prometheus exporter URL to pull metrics from.
+  -metric-prefix string
+        Metric name prefix, only supported by line protocol output formats.
+  -output-format string
+        The check output format to use for metrics {influx|graphite|json}. (default "influx")
+  -prom-query string
+        Prometheus API query string. (default "up")
+  -prom-url string
+        Prometheus API URL. (default "http://localhost:9090")
+```
+
+Application instrumentation:
+
 ```shell
-$sensu-prometheus-collector -exporter-url http://localhost:8080/metrics
+$ sensu-prometheus-collector -exporter-url http://localhost:8080/metrics
 go_memstats_last_gc_time_seconds value=0.000000 1506991233
 go_memstats_mspan_sys_bytes value=32768.000000 1506991233
 ...
 ```
 
 ```shell
-$sensu-prometheus-collector -exporter-url http://localhost:8080/metrics -output-format graphite -metric-prefix foo.bar.
+$ sensu-prometheus-collector -exporter-url http://localhost:8080/metrics -output-format graphite -metric-prefix foo.bar.
 foo.bar.go_memstats_stack_inuse_bytes 294912.000000 1506991405
 foo.bar.go_memstats_mallocs_total 6375.000000 1506991405
 ...
 ```
 
+Prometheus query API:
+
 ```shell
 $sensu-prometheus-collector
 up,instance=localhost:9090,job=prometheus value=1.000000 1506991495