chore(travis): Add ap-get update

Author: ehdsouza

.travis.yml

@@ -20,6 +20,7 @@ script:
 before_deploy:
 - pip install -r requirements.txt
 - pip install -r requirements-dev.txt
+- sudo apt-get update
 - pip install pypandoc
 - sudo apt-get install pandoc
 - pip install --editable .