`mongo-object` NPM package as peer dependency

[manueltimita]

The package aldeed:simple-schema also depends on mongo-object. AutoForm is used in conjunction with SimplSchema more often than not. So both packages end up including the same dependency twice in the final bundle.

Any reasons not to use the peer npm meteor approach?

@jankapunkt I am happy to send a PR. I'm just checking whether there is a known issue / reason why this hasn't been done.