matplotlib Code

Slight documentation changes.

Fix to is_scalar plus additional functions in cbook.py:

less_simple_linear_interpolation
isvector
vector_lengths
distances_along_curve
path_length
is_closed_polygon

fixed is_scalar -- good catch david

Moved unmasked_index_ranges from lines.py to cbook.py

Add deprecation warning to cbook.popd

Cleanup in delete_masked_points

Expanded delete_masked_points to handle more types of argument

Move delete_masked_points() from axes.py to cbook.py so that it's available to more places.

Fixing bug in is_sequence_of_strings.

Making a number of changes related to "blocking" stuff:

1) Adding to cbook.py a method is_sequence_of_strings that is then used in
BlockingInput to test for a tuple-like sequence of event names

2) Modified the use of *fmt* in clabel so that it an also be a
dictionary matching contour levels to arbitrary strings.

3) Removing the extraneous np.array or np.asarray commands in ContourLabeler
as they were forcing linecontour to array, but linecontour should already
be an array.

4) In blocking_input.py replacing all print commands with calls to
matplotlib.verbose.report

5) Removing extra cleanup call from BlockingInput as finally is always
executed, regardless of exception status.

6) Removing what appears to be a "patch" command screwup - there were two
versions of several of the Blocking* classes in blocking_input.py