Use new pep8 on Travis

.travis.yml

@@ -15,12 +15,11 @@ before_install:
   - conda update --yes conda
 
 install:
-  - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then conda create --yes -q -n pyenv mkl python=2.6 numpy=1.6.2 scipy=0.11 nose=1.1 pyparsing=1.5 pip; fi
-  - if [[ $TRAVIS_PYTHON_VERSION == '3.3' ]]; then conda create --yes -q -n pyenv mkl python=3.3 numpy=1.9.1 scipy=0.14.0 nose=1.3.4 pip; fi
+  - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then conda create --yes -q -n pyenv mkl python=2.6 numpy=1.6.2 scipy=0.11 nose=1.1 pyparsing=1.5 pip flake8==2.3; fi
+  - if [[ $TRAVIS_PYTHON_VERSION == '3.3' ]]; then conda create --yes -q -n pyenv mkl python=3.3 numpy=1.9.1 scipy=0.14.0 nose=1.3.4 pip flake8==2.3; fi
   - source activate pyenv
   - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then pip install pydot; fi
   - pip install . --no-deps --use-mirrors
-  - pip install flake8 
 
 # command to run tests
 env: