Merge branch 'v1.3.x'

* v1.3.x:
  Document API change in hist
Fixed typo in TimerWx
Merge branch 'master' of github.com:matplotlib/matplotlib

* 'master' of github.com:matplotlib/matplotlib: (90 commits)
  added information regarding new spectrum functions to CHANGELOG, whats_new, and api_changes
  add demo for new spectral plot types
  add tests for new spectrum types in _axes
  add more spectral plots and add new spectrum types to specgram in _axes
  implement tests for refactored mlab spectrum, windowing, and detrend functions, with 100% coverage
  refactor mlab spectrum, window, and detrend functions to improve modularity, testability, and performance
  add CleanupTestCase, a unittest.TestCase with cleanup
  add mlab tests for new spectrum types, window and detrend functions, and greatly expand existing tests
  add more spectrum functions and add new spectrum types to specgram in mlab.py, and clean up window and detrend functions in mlab.py
  Fix for compiling ttconv in extern directory
  cast argv to unicode before testing
  Move external libraries to 'extern' directory
  Minor doc fixes
  Fix encoding issues when font name contains non-ascii characters
  Fix writing to all manner of StringIO-like objects in PS backend.
  add new ps backend test file in `__init__.py`
  BUG: Fixed object type missmatch in SymLogNorm
  add failing test: savefig(StringIO(), format="ps")
  Adding a missing 'b' back into two 'bbox_' kwargs
  Fix build
  ...
Various path effects related updates.
removing items from the call to six.iteritems
Merge pull request #2553 from fariza/gtk_save_iteritems

removing items from the call to six.iteritems
Merge branch 'master' of github.com:matplotlib/matplotlib

* 'master' of github.com:matplotlib/matplotlib:
  removing items from the call to six.iteritems
  fix removed api change regarding spectral functions
  - pep8  - removed mutable default values  - foo == None -> foo is None
  pep8
Merge remote branch 'upstream/v1.3.x'

* upstream/v1.3.x:
  Update version to 1.3.1
  tiny correction of matplotlibrc.template
  minor docstring fix in dates.py
  Updated the docs of pyplot.gca.
  Fix #2472: Draw the spines on top of twin axes
  changes to c++ because gcc 4.8 seems to allow things the compiler on travis will not.
  added class variable `_fill_color` to RendererAgg to hold the color to use in `clear` calls to the render_base.
  patch to fix issue #2473.

Conflicts:
	lib/matplotlib/__init__.py
	lib/matplotlib/axes/_axes.py
Major refactor of path effects hook. Makes life much simpler!
fixed an enconding bug when checking for gs version
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
fix typo
simplify creation of transparent legend
Merge pull request #2562 from esc/minor_recipe_tweaks

Just some small tweaks to the recipes
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