Added documentation to group dsl

Author: Jeremy Carroll

Diff for: samples/group/README.md

@@ -0,0 +1,15 @@
+This functionality requires [Graphite 1.0] to be
+compiled. The current stable release does not have the
+function groupByNode. This feature will be available
+when Graphite 1.0 is released.
+
+[http://graphite.readthedocs.org/en/1.0/functions.html]
+
+The callback aggregator is a function will be applied
+to the result of groups returned. In this example the
+group will be the hard disk name (Ex: sda1). The 
+function "sumSeries" will be applied to each result 
+adding the total read iops of all like named disks
+and graphing the result.
+
+[1]: http://graphite.readthedocs.org/en/1.0/functions.html        "Graphite 1.0"