DOC/ENH : get/set_size_inches

Added links between `get_size_inches` and `set_size_inches`

Added an `np.array` call to `get_size_inches` to return a copy of
the size, instead of a reference to the internal np.array.

Closes #2303
BUG : Qt repaint workaround on windows

Added platform specific replacement of `update` with `repaint` in
`FigureCanvasQtAgg.draw` for windows.
DOC : minor tweaks to set/get_size_inches

 - better numpydoc style
 - added inch <-> cm conversion factor
DOC : add link to `plt.subplots` from `Figure.add_subplot`
DOC : removed line about un-needed dependencies in Windows

We no longer bundle `dateutil` or `pyparsing`.
colors: Replace docstring ''' with """
test_colors: Fix typo
colors: Add power-law normalization
power_norm_demo: Initial commit
hist2d: Add a note mentioning PowerNorm
Merge pull request #2844 from tacaswell/qt_win_specialcase

BUG : Qt repaint workaround on windows
Don't close figure if context and apply_rcparams are both set. Fixes #2890.
Radius fix in _path.cpp

Updated the points_in_path method to allow negative radii as is implied by the documentation.
adding the linewidth keyword argument to pie
#2899 Adding kwargs to pie which can handle args for both wedge and text elements separately
#2899 almost final changes for adding wedge and text kwargs to pie. needs feedback on generated pyplot
cleaning up code. Added tests and test images
removing empty line for pep8 test
BUG: Removes iteration over locals (no-no) in mathtext
fixing pyplot.py generating boilerplate code to avoid unicode strings