Fix of macosx text rendering truncation with edit 
of _macosx to overcome change in Py_UNICODE size
that occurred in Python3.3
Rollback of error introduced in 
GraphicsContext_draw_image from previous commit.
re-added lines to make sure that `bottom` and `left` are not None in
the case of `log=True`.  If this is not done, there will be type
exceptions.

Issue #1882
simplified logic related to bottom=None and log in `bar`
All changes wrapped by preprocessor directive PY33 to make backward compatible.
All changes wrapped by preprocessor directive PY33 to make backward compatible.
Wrapped #ifdef to make backward compatible.
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