Invalid type specification for Token.for_scope/1

[nicolasgarnil]

Problem

The type specification for the method Token.for_scope/1 specifies that it can return an :error atom but it never does

Solution

In which cases can Token.for_scope/1 return an error? If it can actually can return an error then it should be handled, if not, the type specification should be removed

[peburrows]

Closing as this was resolved by #34.