Fix compilation on Solaris
BUG: Fixed object type missmatch in SymLogNorm

Currently SymLogNorm accepts both linthresh and vmin, vmax with their
native dtype, meaning that the contents of one object cannot be updated
with another due to a mismatch of types.
Merge branch 'v1.3.x'

* v1.3.x:
  Document API change in hist
BUG: fixed shape validation for manual conf intervals in boxplots
TST: fixed new test and added baseline PNG
Install numpy as a setup_requires dependency so pip will install Numpy first
Fix installing numpy as a setup-time dependency
Add tests for installing into a completely clean virtual environment.
Python 3 fixes
Rename C++ variables to avoid use of reserved identifiers
Merge pull request #2445 from mdboom/numpy-setup-dependency

Declare Numpy as a setup dependency
Fix #2300: deal with the case where there are no writable directories.
Fix #2425: setters without arguments should not be added to the list of
parameters
Fix #2418: Crash in PDF backend due to complicated clipping pattern.
Fail hard and fast if the testing data is missing
Merge pull request #2425 from mdboom/axis-off-extra

DOC: `axis_off` wrongfuly appears as a parameter to Figure.add_subplot
Merge pull request #2418 from mdboom/pdf-parent-check

AssertionError with quiver, quiverkey, and an additional patch.
Merge pull request #2379 from mdboom/better-message-about-missing-test-data

Make matplotlib.test() print meaninful messages when baseline images are not installed
Updating version to 1.3.1rc1
BUG: gswin64c.exe not detected on Windows

Move the try/except statement into the loop in order to continue, not break, the loop when an exception occurs.