Add proxy_read_timeout
Replaced params references with config.
Added 4 proxy parameters.
client_body_buffer_size
proxy_connect_timeout
proxy_read_timeout
proxy_send_timeout

And reference these variabels in the template.
Fix validation of events_use parameter
Merge pull request #329 from saz/patch-2

Fix validation of events_use parameter
Merge pull request #326 from janorn/proxy_conf

Make proxy variables configurable via hiera
Add super_user option to be able to launch nginx as unprivileged user without complains.
Validate boolean config option.