Needs @discardableResult added to func stub

[mrkite]

Xcode 8 throws tons of warnings along the lines of "Result of call to 'stub(condition:response:)' is unused".

Since ignoring the return value is totally fine if you don't intend to call removeStub, you should mark the function with @discardableResult and save us from the warning spam.

[Ashton-W]

What Seift versions are compatible with that annotation?

A Pull Request would be great :)

[ikesyo]

What Swift versions are compatible with that annotation?

@discardableResult is for Swift 3, not compatible with Swift 2.3 (that is almost same as Swift 2.2).

[AliSoftware]

Closing this as it's been addressed a while ago by #203 😉