tests: support for Python-3.4

* Adds Python 3.3 and 3.4 to `tox` and Travis CI tests.  (see #17)

* Comments out `cloud` that is not Python-3 friendly.  (see #15)

* Adds Python-3.4 to package classifiers.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>