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?

Author: endolith

doc/users/pyplot_tutorial.rst

@@ -110,10 +110,10 @@ dashes			sequence of on/off ink in points
 data			(np.array xdata, np.array ydata)
 figure			a matplotlib.figure.Figure instance
 label			any string
-linestyle or ls		[ '-' | '--' | '-.' | ':' | 'steps' | ...]
+linestyle or ls		[ ``-`` | ``--`` | ``-.`` | ``:`` | ``steps`` | ...]
 linewidth or lw		float value in points
 lod			[True | False]
-marker			[ '+' | ',' | '.' | '1' | '2' | '3' | '4'
+marker			[ '+' | ',' | '.' | '1' | '2' | '3' | '4' ]
 markeredgecolor or mec	any matplotlib color
 markeredgewidth or mew	float value in points
 markerfacecolor or mfc	any matplotlib color