Explain that matplotlib must be built before the HTML documentation

Attempting to generate the HTML documentation right after cloning the
repository results in a cryptic error message as one of the required
files, mpl-data/matplotlibrc, is created when matplotlib is built. It
seems that other people have come across this problem in the past [1],
so mentioning it here might be of help to newcomers.

[1] http://sourceforge.net/mailarchive/message.php?msg_id=21478615
Add numpydoc to the list of extensions.
Added the autosummary extension module for sphinx
ENH Made the docutils tables generated with the numpydoc in the documentation a little prettier
Show custom error message if we don't have a matplotlibrc file

Even if the README.txt file explicitly mentions that matplotlib must
have been built before the documentation can be generated, a better
error message will be of help to those developers who happen not to
read it.
Show custom error message if we don't have a matplotlib installation
Mention that matplotlib must be installed before building the docs
Revert "When using nearest neighbor interpolation and not actually scaling, just copy the data.  (Note we don't do this for other kinds of interpolation, because the filtering on those interpolations could have an effect even when not actually scaling.)"

This reverts commit 1c9f9b5f6cb3b308df95e56f7230d71963837812.
Partial revert of 8c25664fcfcb9c2e288607ff86d0a1957248284f

This removes the flipping done in Python and keeps the regression tests.
Removed numpydoc
Added documentation on numpydoc
fixes Issue #1693

Explicitly trim rgbFace to length 3 so that the string formats do
not blow up.
Fixed code added in 0c20b5c8013f93147c221f7c035f465c7825d10b
(PR #1505).

Tests added is #1663 pass with this patch.
updated the way the line color + alpha is handled to match how it is
done for markers.  If a 4-tuple is passed in, the alpha from that will
be used, with the kwarg alpha over-ridding it.
Updated the alpha/translucent test to also test lines and a mix of
setting alpha via color and via kwarg
Merge pull request #1694 from tacaswell/ps_backend_fix

fixes Issue #1693
Merge pull request #1660 from vterron/master

Explain that matplotlib must be built before the HTML documentation
Merge pull request #1665 from NelleV/MEP10

MEP10: adding numpydoc and activating autosummary
Fixed doc dependency on numpy_ext.numpydoc
Merge pull request #1696 from pelson/numpydoc_fix

Fixed doc dependency on numpy_ext.numpydoc