Add rickshawGraph proerty to the Graph object. (#2438)
Add rickshawGraph proerty to the Graph object. (#2438)

Add rickshawGraph property to the Graph object.

This allows further changes to be made to the graph, for example,
annotations.


JavierZunzunegui/prometheus,GoogleCloudPlatform/prometheus,AlekSi/prometheus,Stackdriver/stackdriver-prometheus,keegancsmith/prometheus,SaltedMan/prometheus-annotated,Conorbro/prometheus,brancz/prometheus,Conorbro/prometheus,kangwoo/prometheus,Gouthamve/prometheus,yanghongkjxy/prometheus,Stackdriver/stackdriver-prometheus,AlekSi/prometheus,GoogleCloudPlatform/prometheus,JavierZunzunegui/prometheus,alileza/prometheus,keegancsmith/prometheus,dsymonds/prometheus,gottwald/prometheus,yanghongkjxy/prometheus,yanghongkjxy/prometheus,dsymonds/prometheus,yanghongkjxy/prometheus,JavierZunzunegui/prometheus,tomwilkie/prometheus,gottwald/prometheus,alileza/prometheus,Gouthamve/prometheus,prometheus/prometheus,amorken/prometheus,keegancsmith/prometheus,Conorbro/prometheus,keegancsmith/prometheus,kzittritsch/prometheus,brancz/prometheus,Conorbro/prometheus,GoogleCloudPlatform/prometheus,kzittritsch/prometheus,gottwald/prometheus,dsymonds/prometheus,kangwoo/prometheus,Colstuwjx/prometheus,prometheus/prometheus,Gouthamve/prometheus,AlekSi/prometheus,GoogleCloudPlatform/prometheus,AlekSi/prometheus,GoogleCloudPlatform/prometheus,agaoglu/prometheus,tomwilkie/prometheus,keegancsmith/prometheus,prometheus/prometheus,tomwilkie/prometheus,Colstuwjx/prometheus,Stackdriver/stackdriver-prometheus,Colstuwjx/prometheus,brancz/prometheus,prometheus/prometheus,kangwoo/prometheus,kzittritsch/prometheus,SaltedMan/prometheus-annotated,amorken/prometheus,tomwilkie/prometheus,Colstuwjx/prometheus,kzittritsch/prometheus,kangwoo/prometheus,brancz/prometheus,gottwald/prometheus,SaltedMan/prometheus-annotated,alileza/prometheus,Gouthamve/prometheus,prometheus/prometheus,Stackdriver/stackdriver-prometheus,amorken/prometheus,JavierZunzunegui/prometheus,dsymonds/prometheus,SaltedMan/prometheus-annotated,agaoglu/prometheus,amorken/prometheus,agaoglu/prometheus,alileza/prometheus,alileza/prometheus,agaoglu/prometheus