Add optional support to log path params

[jonathansamines]

hapi-pino binds the request only once during the onRequest hook:

https://github.com/pinojs/hapi-pino/blob/27806507920fda5db27c2daca0a99259423ba647/index.js#L111-L118

However, hapi only makes request.params available later in the request lifecycle, and it is accessible only after onPreAuth at the earliest. This pull request adds optional support to log pathParams when logPathParams is true, in pretty much the same way that logQueryParams works

[coveralls]

Coverage decreased (-99.07%) to 0.0% when pulling 27b2751 on jonathansamines:feature/optional-path-params-log into 2780650 on pinojs:master.

[mcollina]

lgtm