Improve specifying of http options

@TabDigital/api 

This PR fixes the following issue https://github.com/TabDigital/hyperactive/issues/1
It allows you to pass in any `unirest` option
They have a link straight to options in their docs so we could link to that?

*Note:* `hyperactive` uses [unirest](https://github.com/Mashape/unirest-nodejs) to send requests.
The `options` hash can contain [any valid Request option](https://github.com/Mashape/unirest-nodejs#requestoptions) from unirest.