update travis config

Author: chfw

.travis.yml

@@ -13,6 +13,7 @@ install:
   - if [[ $TRAVIS_PYTHON_VERSION == "2.6" ]]; then pip install ordereddict; fi
   - pip install git+https://github.com/chfw/pyexcel-io.git  
   - pip install git+https://github.com/chfw/pyexcel.git
+  - pip install -r requirements.txt
   - pip install -r tests/requirements.txt
 script:
   make test