Add vm-browserify

[cusspvz]

https://github.com/browserify/vm-browserify/

[parshap]

This isn't going to work in a React Native environment because it depends on document.createElement('iframe'): https://github.com/browserify/vm-browserify/blob/6b0773a7a2e2e0d67b9ee7f31102d3e635bf00b1/index.js#L61

I think a mock implementation for vm is more appropriate, where the api is mocked out but there is no implementation.

[cusspvz]

https://github.com/requirehit/native-vm