Todo : Add yAxis Max to Graph

[draco2003]

Some metrics have very high spikes which skew the graphs. It would be nice to have a yAxis Max at the graph level to fix this.

Graphite uses the following url attribute to add this:
&yMinLeft=

[ssandler]

This is possible now with the custom options from issue #9, up to you on whether it's worth it to also add specific y-axis params as well or just close out this issue.