Assumes process implies process.versions.node

We are simulating `process` in the browser using https://github.com/defunctzombie/node-process/blob/master/browser.js . It doesn't have `process.versions.node` in it, so this check over here gives an error: https://github.com/keyz/identity-obj-proxy/blob/master/src/index.js#L10

It would be nice if the code were updated to handle the case where `process.versions.node` is set even if `process` is not.

Start by inspecting src/index.js at line 10 and compare its assumption about process.versions.node with the browser process shim linked in the issue. Reproduce the error with that shim, then verify the check no longer fails when process.versions.node is absent.

Written by the indexing model from the issue text.