Fixes issues with uchiwa 0.3.2

Previous PR shipped uchiwa 0.3.2 however some behaviour skipped
my attention. Uchiwa uses websockets so we need to get our nginx
to upgrade the connection to Websocket when proxying. Also uchiwa
needs to point to public HTML directory via -p switch.
Make sure sensu.conf nginx config is no longer present after upgrade

Also updated formula-requirements dependencies
Upgrade uchiwa to 0.3.2
Merge pull request #46 from ministryofjustice/uchiwa-fix

Fixes issues with uchiwa 0.3.2