Add options to NahmiiProvider

[hubiierik]

When creating a NahmiiProvider
I would like to give it some options
in order to control how the underlying transport layer is working.

Currently we only want to control the timeout parameter of
superagnent. We could require only the timeout parameter in the constructor but it is probably useful to send the options wrapped in an object so that options can be added in the future.

This feaure will also affect the internal object NahmiiRequest,