Fix broken pip command for Travis

.travis.yml

@@ -9,7 +9,7 @@ cache:
     directories:
         - $HOME/.cache/pip
 install:
-    - pip --upgrade pip setuptools wheel
+    - pip install --upgrade pip setuptools wheel
     - pip install -r .requirements-full-test.txt --only-binary=numpy,scipy
 script:
     - py.test test/