Module instance lacks "paths" property

Usually, a NodeJS `module` will have a `paths` property. Unfortunately, the current implementation of `Module` class does not have it, and since some npm packages may assume its existence, this results in runtime errors, e.g.

https://github.com/mochajs/mocha/blob/master/lib/mocha.js#L28

In this case `import 'mocha'` results in:

```
TypeError: Cannot read property 'push' of undefined
at meteorInstall.node_modules.mocha.lib.mocha.js (node_modules/mocha/lib/mocha.js:29:1)
at fileEvaluate (packages/modules-runtime/.npm/package/node_modules/install/install.js:153:1)
```