round up maxDataPoints to nearest integer in request. graphite 0.9.x and...

... 0.9.12 seem to treat decimal maxDataPoints badly returning enourmous amounts of data.

I was messing around with using the 30day dashboard time range and noticed that it was exceedingly slow. After some digging I found that if you pass a decimal to graphite for maxDataPoints it returns a massive time range, seemingly all the data for that range at the smallest resolution.
Although this seems like a graphite issue, the client side fix is quite simple so I figured I'd contribute.