Allow credentials to be passed up to allow securing behind phoenix pipelines

[mgwidmann]

The following does not work:

scope "/admin" do
  pipe_through :admin

  forward "/wobserver", Wobserver.Web.Router
end

All JSON api requests end up being denied because no cookies are sent and so therefore cannot be validated.

[coveralls]

Coverage remained the same at 99.716% when pulling 5d69ac6 on mgwidmann:include_credentials into 7c6186b on shinyscorpion:master.

[mgwidmann]

I'm not sure that my changes actually caused those errors, did they?

[mgwidmann]

bump any thoughts on this? Its quite annoying to build this from source every time...

[mgwidmann]

can we get some movement on this PR?

[langalex]

looking at master, the build was already broken, so it wasn't you @mgwidmann.

[langalex]

most of the breakage occurred with this "Update dependencies." commit