Service rating dashboard

Spec: https://docs.google.com/a/praekeltconsulting.com/file/d/0B7R1YAPd1mwcelp6d3BYcDdJRFk/edit

Build in Sapphire: http://sapphire.readthedocs.org/en/latest/

Example in action: http://bl.ocks.org/justinvdm/5d2b4bc4df71d1027e97

Needs to display:

- [ ] Total responses in x (24 hours, 7 days, last month, ever)
- [ ] Same by clinic code (optional)

Add link to new view in custom admin link: https://github.com/praekelt/go-rts-zambia/pull/98/files