Update README.md

Author: yaacov

README.md

@@ -53,6 +53,8 @@ prometheus = Prometheus::ApiClient.client(url:         'https://example.com:443'
 
 #### High level calls
 
+###### query
+
 ```ruby
 
 # send a query request to server
@@ -63,6 +65,8 @@ prometheus.query(
 )
 ```
 
+###### query_range
+
 ```ruby
 # send a query_range request to server
 prometheus.query_range(
@@ -104,6 +108,8 @@ prometheus.query_range(
                [1502086470.781, "53892.665282065"]]}]}
 ```
 
+###### label
+
 ```ruby
 # send a label request to server
 prometheus.label('__name__')
@@ -113,13 +119,18 @@ prometheus.label('__name__')
  "kubernetes-service-endpoints"]
 ```
 
+###### targets
+
 ```ruby
 # send a targets request to server
 prometheus.targets()
 ```
 
 #### cAdvisor specialize client
 
+A cAdvisor client is a client that add object specific labels to each REST call,
+objects available are Node, Pod and Container.
+
 ```ruby
 
 # create a client for cAdvisor metrics of a Node instance 'example.com'