[Matplotlib-users] New autoscaling and offset capabilities for collections

Potential testers:

CVS mpl now has a new demo (examples/collections.py) that illustrates 
two minor new capabilities:

1) The axes.add_collection() method accepts a new boolean kwarg, 
"autolim"; if True, then a subsequent call to axes.autoscale_view will 
take into account the data in the collection.

2) LineCollection can now be called with kwargs
      "offsets=(xo,yo), transOffset=None"
to facilitate making waterfall plots or stagger plots--that is, a set of 
sequentially offset curves.

The demo may also be useful in illustrating some basic ways of using 
line and polygon collections; this is not entirely obvious from the 
docstrings.  (I have tried to improve some of the docstrings also.)

The changes were prompted by Chris Barker's earlier message with a demo 
script, which showed me how to use the two transforms involved in these 
types of collections.

Eric