added 'savefig.transparent' rcParams

Closes issue #2388
minor tweak to `pyplot.savefig` to ensure that if `transparent=True`
is passed to `savefig`, the patch colors are restored on the screen
after saving.
Merge pull request #2383 from cgohlke/patch-1

BUG: Fix IndexError: too many indices with numpy 1.8
comment tweak

As suggested by @dmcdougall
Added entry to whats_new.rst
Merge pull request #2390 from tacaswell/transparent_rcparams

Transparent rcparams
use six.move for cStringIO
Only test png and remove test text
Merge pull request #2372 from neggert/hist_endline_fix

Fix step histogram endline
Be more careful about setting the locale
Merge pull request #2393 from davidovitch/use_stringIO_from_six

use six.move for cStringIO
Merge pull request #2331 from megies/optional_backend_config_check

Make optional backends respect setup.cfg
Merge pull request #2396 from mdboom/locale-try

Try UNIXy and Windowsy ways of setting locale
TypeError occurs when self.button=None in MouseEvents
support tight_bbox for pgf output, fixes #2342
Merge pull request #2391 from pwuertz/fix_2342

 support tight_bbox for pgf output, fixes #2342
support tight_bbox for pgf output, fixes #2342 (v1.3.x)
Merge pull request #2402 from pwuertz/fix_2342

support tight_bbox for pgf output, fixes #2342 (v1.3.x)
Merge pull request #2399 from dimkal/master

TypeError occurs when self.button=None in MouseEvents
Fix ps backend from 2to3->six changes