Add scraper for Prometheus clients (#47)

receivers/prometheusReceiver.md

@@ -0,0 +1,27 @@
+## `prometheus` receiver
+
+The `prometheus` receiver can be used to scrape the metrics of a single `prometheus` client. It does **not** use any official Golang library but making simple HTTP get requests and parse the response.
+
+### Configuration structure
+
+```json
+{
+  "<name>": {
+    "type": "prometheus",
+    "address" : "testpromhost",
+    "port" : "12345",
+    "port" : "/prometheus",
+    "interval": "5s",
+    "ssl" : true,
+  }
+}
+```
+
+- `type`: makes the receiver a `prometheus` receiver
+- `address`: Hostname or IP of the Prometheus agent
+- `port`: Port of Prometheus agent
+- `path`: Path to the Prometheus endpoint
+- `interval`: Scrape the Prometheus endpoint in this interval (default '5s')
+- `ssl`: Use SSL or not
+
+The receiver requests data from `http(s)://<address>:<port>/<path>`.