Merge pull request #186 from lpsinger/python3

Add support for Python 3.2, 3.3, 3.4
Test multiple Python versions with Travis

Based on <http://conda.pydata.org/docs/travis.html>. Test with both
Anaconda and native Ubuntu Python interpreters.
Don't use C99 designated initializers

It causes some build failures in Travis CI.
Wrap travis_retry around pip commands

Sometimes there are network glitches which cause `pip` to fail with the
message `Connection reset by peer`. If we wrap `pip` commands with
`travis_retry`, these commands will be tried up to three times before
causing a build failure.

See <http://docs.travis-ci.com/user/build-timeouts/>.
Skip Python 3.4 if not using Anaconda

The Ubuntu package used by Travis seems to use different default
compiler flags.