[Rivet] mcplots

[Peter Skands]

Hi again,

> - Can you plot the tick marks in the ratio plots on top of the error
>    bands, rather than below?

I just remembered I got so annoyed with this Root "feature" also, that I 
actually did make a small workaround, which should already be visible on the 
current dev site. I added a slight inner margin to the plots, in particular the 
ratio ones, such that the tick marks are always at least partially visible. This 
should help alleviate the visual part of the problem.

Peter