Issue #783: python3 compatible - do not instruct travis to install six.

.travis.yml

@@ -11,7 +11,6 @@ before_install:
   - sudo apt-get install -qq libatlas3gf-base libatlas-dev
 install:
 # If we don't install numpy before SciPy 0.10.1, the SciPy installations fails.
-  - "pip install -q six==1.2.0 --use-mirrors"
   - "pip install -q numpy==1.5 --use-mirrors"
 # We can't install SciPy as there is no BLAS installed.
   - "pip install . --no-deps --use-mirrors"