Use Dask 0.7.1 on Python 3.2

Try dask 0.7.2

Try dask 0.7.1

Fix comment

tools/travis_before_install.sh

@@ -52,9 +52,10 @@ source ~/venv/bin/activate
 pip install --upgrade pip
 pip install --retries 3 -q wheel flake8 coveralls nose
 
-# on Python 3.2, use matplotlib 1.3.1
+# on Python 3.2, use older versions of matplotlib and dask
 if [[ $TRAVIS_PYTHON_VERSION == 3.2 ]]; then
     sed -i 's/matplotlib>=.*/matplotlib==1.3.1/g' requirements.txt
+    sed -i 's/dask.*>=.*/dask[array]==0.7.1/g' requirements.txt
 fi
 
 # install wheels