Fix for issues #461 and #471.

Upgraded c-ares to 1.10.0

This handles None exception values that would otherwise fail when passed
to traceback.print_exception() and prevent the process from exiting. An associated test is also included.

One test in test_threading.py fails under PyPy 2.6; that test has been removed from upstream (https://bitbucket.org/pypy/pypy/diff/lib-python/2.7/test/test_threading.py?diff2=4ecd94a66a87&at=vendor/stdlib) so don't run it here either. I'm not updating the whole module yet because we run tests under 2.5.0 on Travis.

subprocess.Popen `bufsize` option actually used

Use the TravisCI container infrastructure and enable linters

Previous debugging shows the socket accepting all the data we send it, which is just under 2MB. Maybe travis containers have very large default socket buffers? Up the data size to about 4MB.

Pre-allocate the (biggec) data before we start taking timing measurements, and be sure to close the socket when done.