Added space key and access token to example.
Added space key and access token to example.

Makes it clear how to use them from the start.
davidmdavis/contentful.objc,davidmdavis/contentful.objc,contentful/contentful.objc,akfreas/contentful.objc,davidmdavis/contentful.objc,contentful/contentful.objc,contentful/contentful.objc,akfreas/contentful.objc,danieleggert/contentful.objc,akfreas/contentful.objc,danieleggert/contentful.objc,danieleggert/contentful.objc