Error occuring on authentication of non embeded app

[julesbl]

When using the package for OAuth of an offline/not embedded app, the function OAUTH::callback() attempts to use setcookie() with a null value for expires: parameter.

The same issue was raised here
#291
This issue is still extant as the pull request failed, I made the changes indicated and it works, however if I update my version I will be back to a fail again.