Replaced lsmod by package-list

When using tools like `pm2`, the method used by `lsmod` is not capable of detecting the packages of the child process. This means that sentry will always receive the list of modules of pm2 and not of your project's own dependencies.

Here's an example for a project using `foo` and `package-list`as dependencies, plus `lsmod` installed but not added to the project's `package.json`:

```
Output from `lsmod`:
{ pm2: '0.7.7', 'coffee-script': '1.7.0' }
------
Output from `package-list`
{ foo: '1.0.0',
  'package-list': '0.0.1',
  lsmod: '0.0.3 (extraneous)' }
```

This is up for discussion as the async nature of `getModules` changes the return values of some functions.