[WIP] Support for `Uchiwa`, a dashboard for `sensu`

- [ ] Support for `Uchiwa`, a dashboard for `sensu`
Introduce `Uchiwa`, a dashboard for `Sensu`

- Add dependency on `Uchiwa` cookbook.
- Install `Uchiwa`, a dashboard for `Sensu`.

```
--- a/site-cookbooks/sensu-custom/recipes/default.rb
+++ b/site-cookbooks/sensu-custom/recipes/default.rb
@@ -24,6 +24,7 @@ if node["sensu-custom"]["server"]
   include_recipe "sensu::api_service"

   include_recipe "nginx"
+  include_recipe "uchiwa"

   include_recipe "sensu-custom::server_settings"
```