Enable log based metrics for nova

New prometheus metrics now available:

  * log_messages - total number of log lines per severity
  * openstack_http_response_times - set of HTTP-stats metrics per HTTP method and status:
    - three quantiles, 50%, 90% and 99% for response time
    - sum of response time
    - count of responses

Change-Id: I60b104b3d3579c99616d24c23de02c72c265e5a4
diff --git a/README.rst b/README.rst
index d6283be..8f773a7 100644
--- a/README.rst
+++ b/README.rst
@@ -653,9 +653,9 @@
   * openstack_log_appender - set it to true to enable log_config_append for all OpenStack services;
   * openstack_fluentd_handler_enabled - set to true to enable FluentHandler for all Openstack services.
 
-Only WatchedFileHandler and FluentHandler is available.
+Only WatchedFileHandler and FluentHandler are available.
 
-Also it is able to configure this with pillar:
+Also it is possible to configure this with pillar:
 
 .. code-block:: yaml