config: adds demosite specifc configuration

* Adds module with demosite specific configuration.

* Adds config module in entry point, allowing it to be loaded
  automatically by Invenio.
Merge pull request #6 from lnielsen-cern/pu-site-config

config: adds demosite specifc configuration
Merge pull request #4 from jirikuncar/pu-travis

Travis integration and installation fixes
ranker: fix default knowledge base value
Merge pull request #8 from jirikuncar/pu-ranker-config-fix

ranker: fix default knowledge base value
travis: installation process improvement