Go back to one ghostscript process per test
Fix some test images that weren't being run on Travis before
Run tests in parallel on Travis and in tox
Include all test files
Make the test function name match so that they can be pickled through multiprocessing
Don't call "show" from a test
Fix typo so correct gs executable will be run
Remove import of old util
Don't run tests in parallel on Travis
Use $(nproc) to determine number of processors, as discovered by @pelson.
Use cbook.mkdirs, since with multiprocessing tests each process may try to create a directory at the same time
Make the log quieter
Only compare PNG version of hexbin extent -- it otherwise can crash inkscape on Travis
Don't switch backends in a test
Make pip install of pyparsing quiet also
Limited number of processes on Travis to 8, since otherwise we run out of memory when running too many inkscapes/ghostscripts in parallel
Remove tests we're no longer using because they consume too much memory on Travis
Fix .travis.yml message
Supported datetimes with microseconds, and those with long time series (>160 years).
@NelleV's review actions.