DOC:Use monospace for --

The -- is rendering as an en dash on http://matplotlib.org/users/pyplot_tutorial.html

Maybe all strings should use monospace instead of single quotes?
DOC: Change all strings to ``'monospace'`` in quotes
DOC: Change strings to monospace
add __enter__ and __exit__ to PdfPages
multipage pdf: show usage of with statement in example
Adding possibility to remove invisible lines and patches from relim
Fix merge
docstring fix
Merge pull request #2421 from megies/patch-2

Docstring fix
Merge remote-tracking branch 'upstream/v1.3.x'
Fix some six.moves
Remove dead RMS computation code
DOC: Add axes_api to documentation after the refactoring

Recently, axes was converted from a module to a package.
This adds axes_api to the doctree back.
`show-inheritance` was removed because it tells the user that
`Axes` `Bases: matplotlib.axes._base._AxesBase`
which is not that relevant I think.
This is mentioned in issue #1461
Adding test test_relim_visible_only
DOC: changed axes_api from automodule to autoclass

with automodule we had: `matplotlib.axes._axes.Axes`
while with autoclass we have `matplotlib.axes.Axes`

However, we must remember this documents only one class, so if
classes will be added to the module, they should be added
by hand.
Merge pull request #2426 from mdboom/testing/remove-dead-rms-computation

Remove dead rms computation
Merge pull request #2319 from tacaswell/draw_idle_fix

fix draw_idle reference in  NavigationToolbar2
Merge pull request #2242 from endolith/patch-3

DOC:Use monospace for --
Add webagg api docs
Document API change in hist