plot_utils: let pre_plot_setup setup multicolumn plots
diff --git a/cr2/plot_utils.py b/cr2/plot_utils.py
index 27ba514..cfd0a93 100644
--- a/cr2/plot_utils.py
+++ b/cr2/plot_utils.py
@@ -50,7 +50,7 @@
     """
     set_lim(ylim, ax.get_ylim, ax.set_ylim)
 
-def pre_plot_setup(width=None, height=None):
+def pre_plot_setup(width=None, height=None, ncols=1):
     """initialize a figure
 
     width and height are numbers.  This function should be called
@@ -68,9 +68,9 @@
         if width is None:
             width = height * GOLDEN_RATIO
 
-    _, ax = plt.subplots(figsize=(width, height))
+    _, axis = plt.subplots(ncols=ncols, figsize=(width, height))
 
-    return ax
+    return axis
 
 def post_plot_setup(ax, title="", xlabel=None, xlim="default", ylim="range"):
     """Set xlabel, title, xlim adn ylim of the plot