Search index to be automatically rebuilt whenever documents.py is changed

[ranajaydas]

Problem:
The Heroku app recently showed Server 500 errors upon any search, because I changed documents.py during the hackathon (this file decides how to index the acts and is closely linked to elasticsearch). Every time this file is updated, we should rebuild the index by running python manage.py search_index --rebuild.

Solution:
The search_index must be somehow rebuilt, either on a regular basis or upon every deploy. Exact solution to be evaluated.