Merge remote-tracking branch 'upstream/v1.3.x'
Merge pull request #2550 from joferkington/fix-wx-singleshot-timer

Using a single-shot timer with the Wx backend raises an AttributeError
Merge pull request #2550 from joferkington/fix-wx-singleshot-timer

Using a single-shot timer with the Wx backend raises an AttributeError
fix typo
simplify creation of transparent legend
pep8 fix
pep8 for backend_pdf.py
remove backend_pdf from pep8 test exclude list
minor code standard changes
minor code formatting
Merge pull request #2562 from esc/minor_recipe_tweaks

Just some small tweaks to the recipes
more informative exceptions for empty/not-existing images in
compare_images()
add titleweight rc param
actually read the new rcParam
reference rcparam in docstring for pyplot interface
fix pep8 errors.
Merge pull request #2462 from pelson/path_effects_update

Path effects update
adds rcParam `axes.formatter.useoffset`

Addresses issue #2400

added test for axes.formatter.useoffset rcparam
MultiCursor: make events connected during __init__ accessible (for later removal)
fix operation order error in _spectral_helper and implement more tests to catch these sorts of problems in the future