Fix mono font rendering -- characters are now correctly superimposed.  Primarily affects mathtext.
finish backport of pr 575 for slider fix
use class level rather than instance level caching of fonts to delay the too many open file handles windows bug
slurp down a class level cache into the instance level at the start of draw, and push it back up when done
use threading Lock to protect class level font cache
mplot3D: Change get_zticks to match get_xticks and get_yticks
Merge pull request #809 from jenshnielsen/zticks

Fix get_zticks and docs
Fix issue #804 by altering path clipping
Display progress of tests
Merge pull request #797 from jdh2358/backport-sliderfix

Backport sliderfix
Merge pull request #798 from jdh2358/class-font-cache

use class level rather than instance level caching of fontd
Merge pull request #817 from jkseppan/issue-804

If path clipping introduces MOVETO operations, change final CLOSEPOLY to LINETO
Merge pull request #824 from mdboom/test-progress

Tests don't display progress
Merge pull request #793 from mdboom/mono_fonts

Mono fonts
Fix \prime vs. apostrophe issues.  A bug was introduced in PR #54 where all primes got smaller.  It turns out the correct fix is to keep primes large, but make aprostrophe equivalent to ^{\prime}.
Merge pull request #836 from mdboom/mathtext-prime

mathtext-prime
Updated marker documentation & added example of using a Path with a marker.
Fixed typos.
Added #843's fix
Merge pull request #834 from pelson/marker_doc

Extended marker documentation