Enable Travis CI buildbot

This PR enables the Travis CI buildbot for Scipy, testing Python 2.6, 2.7, and 3.3.

The "fast" test suite completes in less than 10 minutes on Python 2.x and in less than 20 min on Python 3.3 (the difference comes from the dependencies not being preinstalled for Python 3.3). The "full" test suite runs up to ~30 min and is only run for Python 2.7.

Example of the results here: https://travis-ci.org/pv/scipy-work