changing from ubuntu package to pip

.travis.yml

@@ -4,7 +4,7 @@ python:
   - "2.7"
 install:
   - "pip install --allow-all-external -r requirements.txt"
-  - "sudo apt-get install -y npm python-demjson"
+  - "pip install --allow-all-external demjson"
   - "sudo npm install -g js-yaml"
 script:
   - |