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

[ghost]

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

[Rush]

I think it is safe to automatically merge, would make life easier to simply depend on a git version of the gem at least :)

[thegillis]

Would be great to have this merged in. We have needed this for over a year now to get our production precompile to work.

We are using several older libraries that are not module friendly and try to populate the global scope. These will not work without the wrapShim option.