Add tests for oneOfType with shape

[justinj]

This caused issues when there would be a union of a shape checker which
did not pass, and another type which did. The shape checker would output
warnings even though the other type passed.

Also, I signed the CLA.

[sophiebits]

Looks good to me, thanks.

[chenglou]

I've fixed this internally and added your test. The PropTypes are rewritten and no weak is needed anymore.
Will wait for @zpao to sync out, along with your tests.

[chenglou]

@justinj can you rebase this? We've changed PropType a bit. .weak is no longer needed, but the tests are good.

[justinj]

Ok, thanks for fixing that problem :) I rebased the tests.

[zpao]

Thanks @justinj!