.travis.yml: Remove PYTHONPATH and sudo from 'make setup'

The Travis runs currently die with:

  Traceback (most recent call last):
    File "/home/travis/virtualenv/python2.7.8/lib/python2.7/site-packages/nose/loader.py", line 414, in loadTestsFromName
      addr.filename, addr.module)
    File "/home/travis/virtualenv/python2.7.8/lib/python2.7/site-packages/nose/importer.py", line 47, in importFromPath
      return self.importFromDir(dir_path, fqname)
    File "/home/travis/virtualenv/python2.7.8/lib/python2.7/site-packages/nose/importer.py", line 94, in importFromDir
      mod = load_module(part_fqname, fh, filename, desc)
    File "/home/travis/build/thumbor/thumbor/thumbor/integration_tests/__init__.py", line 3, in <module>
      from tornado.testing import AsyncHTTPTestCase
  ImportError: No module named tornado.testing

But we are installing Tornado.  This commit simplifies what we're
doing to try and get successful tests with less magic.