Store the base dir. Used to load modules relative to the root. 

This can be leveraged to load modules in the root/node_modules directory. See

- https://github.com/ryanramage/unpm-auth-ldap
- https://github.com/ryanramage/unpm-auth/commit/39373949c19be453d1ac211ad6c7f05868a88675

For usage.