Drop EOL'd Python 3.3 from Travis builds
Drop EOL'd Python 3.3 from Travis builds

Python 3.3 reached EOL a couple of months ago, and setuptools dropped support
for it earlier this year: pypa/setuptools@7392f01ff . As a result, the 3.3 entry in the
build matrix has been erroring out since at least #196.
berdario/pew,berdario/pew