Update of mlab.pca - updated docstring, added saving the eigenvalues.

The old version of pca class did not save the Eigenvalues - just the "fractions" that are just percentage values.

Also added info which row of Wt one can find the Eigenvectors.
Merge branch 'v1.3.x'

* v1.3.x:
  Document API change in hist
Add "sage" colors to colors.py

A Sage user commented that one couldn't make plots in Sage "sage".  But this is a color.  http://xkcd.com/color/rgb/ recommends the following, and the discussion at https://groups.google.com/forum/#!topic/sage-devel/CnH45Ym4zSk indicates it could be useful as well as fun.
Fix #2423: Clip markers off figure.
fixed an enconding bug when checking for gs version
Consider ourselves interactive if sys.flags.interactive is set.
pep8
- pep8
 - removed mutable default values
 - foo == None -> foo is None
overloaded `_make_twin_axes` on `LocateableAxesBase` so that twinx and
twiny will work.
Add comment
fix removed api change regarding spectral functions
Added methods to control theta position of r-ticklabels on polar plots
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.
Merge pull request #2514 from tacaswell/mpl_toolkit_pep8

Mpl toolkit pep8
Merge pull request #2547 from toddrjen/apideltafix

fix removed api change regarding spectral functions
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