Fix recommended graphite version for better performance

There is no 0.9.13 graphite release, only 0.9.14.

docs/sources/installation/performance.md

@@ -8,7 +8,7 @@ page_keywords: grafana, performance, documentation
 
 ## Graphite
 
-Graphite 0.9.13 adds a much needed feature to the JSON rendering API
+Graphite 0.9.14 adds a much needed feature to the JSON rendering API
 that is very important for Grafana. If you are experiencing slow load &
 rendering times for large time ranges then it is most likely caused by
 running Graphite 0.9.12 or lower.
@@ -17,6 +17,6 @@ The latest version of Graphite adds a `maxDataPoints` parameter to the
 JSON render API. Without this feature Graphite can return hundreds of
 thousands of data points per graph, which can hang your browser. Be sure
 to upgrade to
-[0.9.13](http://graphite.readthedocs.org/en/latest/releases/0_9_13.html).
+[0.9.14](http://graphite.readthedocs.org/en/latest/releases/0_9_14.html).