Renamed incorrecly named build option 'wrap' to 'wrapShim'

According to the RequireJS docs there is a build option called 'wrapShim', but I couldn't find any reference to wrap.

https://github.com/jrburke/r.js/blob/b8a6982d2923ae8389355edaa50d2b7f8065a01a/build/example.build.js#L68