TST: switch i386 build to python3.4 defaulting ubuntu 14.04

python 3.4rc1 is available and we should improve our coverage by switching one of our tests to it.
switching the i386 test to ubuntu 14.04 gives us newer compilers, libc and atlas in addition to python3.4. As 14.04 its still in development mode we might get some false positives due to issues in the distribution, but I think its worth trying.