Fix warning for OS X builds
Fix warning for OS X builds

contentful/contentful.objc,akfreas/contentful.objc,contentful/contentful.objc,akfreas/contentful.objc,danieleggert/contentful.objc,davidmdavis/contentful.objc,davidmdavis/contentful.objc,danieleggert/contentful.objc,akfreas/contentful.objc,danieleggert/contentful.objc,contentful/contentful.objc,davidmdavis/contentful.objc