Minor fix

pip3 does not seem to work. trying with only pip2

.travis.yml

@@ -16,7 +16,6 @@ install:
        ;
     fi
   - sudo -H pip2 install --upgrade nose numpy
-  - sudo -H pip3 install --upgrade nose numpy
 os:
   - linux
   - osx
@@ -28,4 +27,4 @@ env:
 script:
   - mkdir build && cd build
   - cmake -DCMAKE_BUILD_TYPE=RelwithDebInfo .. && make -j4 && make install
-  - cd .. && pip3 install --user . && nosetests --exe -vd tests/test_basic.py
+  - cd .. && pip2 install --user . && nosetests --exe -vd tests/test_basic.py