Remove trailing backslash as pointed out by @dmcdougall
Don't use the font cache on TRAVIS
Merge pull request #2132 from mdboom/font_cache_fix

Attempt to fix Travis tests by not using font cache there.
Add infrastructure for testing of mpl toolkits and a single test to demonstrate.
"python tests.py" runs all tests from mpl and the toolkits.
mpl_toolkits.test() runs tests of the toolkits only.
verbost output from travis. Taken from #1448
add more tests to axesgrid1
include toolkit tests in the documentation