Fix itervalues -> values.  As reported by Massimiliano Costacurta in mailing list thread "BUG: RuntimeError: dictionary changed size during iteration"
slight tweak to the documentation of `errorbar` to make it clear
that xerr and yerr are always relative to the data location.
white space fix
Merge pull request #1743 from tacaswell/errorbar_doc_tweak

slight tweak to the documentation of `errorbar`
Merge pull request #1698 from mdboom/iteritems_bug

Fix bug updating WeakKeyDictionary during iteration
Update examples/pylab_examples/histogram_demo_extended.py

Fixed a variable name typo
Merge pull request #1755 from drevicko/v1.2.x

Update examples/pylab_examples/histogram_demo_extended.py
Improved the subplot function documentation and fixed the autogeneration
from boilerplate.
Merge pull request #1760 from pelson/subplot_doc

Improved the subplot function documentation and fixed the autogeneration from boilerplate.