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
Merge pull request #2399 from dimkal/master

TypeError occurs when self.button=None in MouseEvents
Fix ps backend from 2to3->six changes
backend_pgf: fix str/unicode comparison errors
Merge pull request #2404 from mdboom/ps-backend-encoding

Fix backend_ps.py
Fix syntax error on Python 3.2.
Merge pull request #2407 from pwuertz/fix_unicode_comp

backend_pgf: fix str/unicode comparison errors
removed un-needed legacy code (_AnnotationBase._get_xy_legacy)

All of the work done in _get_xy_legacy can be done via
transforms returned by _get_xy_transform.

Removed the sole usage of this function and the function.
re factored `_AnnoationBase` to push keeping track of there the
secondary object is to the sub-classes.

Added properties to maintain back-compatibility

added properties to replace xytext and textcoords (xyann, anncoords)

properly deprecated `textcoord` and `xytext` in favor of `anncoords`
and `xyann`.
pep8 fixes
added test for Annotation.set_position