Fix syntax highlighting in README.
Fix syntax highlighting in README.

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