Autoscaling and limits in mplot3d.

    * Fixes improper setting of x,y,z limits not turning off autoscaling
    * Adds units support to z-axis
    * Adds shared axis support for z-axis
    * Closes #783
A bit of cleanup
delaunay linear_interpolate_grid: enable grid of height/width 1
fixes #997
PEP8 fixes on dates.py
delaunay: test for 1d and 0d grids (fails upstream) re: issue #997
Merge branch 'iss997_test' into iss997_altfix
Make Axes.stem take at least one argument.

When it takes only one, the abscissae default to np.arange(len(y))
Add axes.stem call signature test
Update CHANGELOG with axes.stem change
test_delaunay: avoid numbers in 1d test, use np.allclose
Merge branch 'iss997_test'
_delaunay.cpp: support [x0:x1:1j] grids even if x1!=x0
Fix positional argument parsing
Make stem catch explicit Exception classes
pyplot.plotfile: forced grid draw removed and documented
PEP8-compliance on axes.py (patch 3 / 4)
ENH: add avconv movie writer for animations
Squashed three commits into one.
TST: add smoke test for saving of animations
str.format() doesn't work on python 2.6