Compatibility with credentialed requests

[Kingson-de]

In order that drakov supports credentialed requests there needs to be some tweaks to the control headers.
For example to use drakov together with the HAL browser this change is needed because the HAL browser can only send credentialed requests.

[yakovkhalinsky]

@Kingson-de thank you for your PR.

Would be interesting to hear about how you are using Drakov.

Merging

[Kingson-de]

@yakovkhalinsky Thanks for this quick merge.
In my company we want to improve an existing API and are currently designing version 2.
So with drakov we have the great opportunity to design this new version with API blueprint and then test it with the HAL browser. Because one of the key features is to use hypermedia and also our app developers can already start working on version 2. Thanks for this great tool it helped us a lot and it was also part of many meetings here :)

[yakovkhalinsky]

@Kingson-de great to hear some feedback!

I'll have this up on npm in the next 24 hours 👍

[Kingson-de]

@yakovkhalinsky perfect!