feat: resolve depndencies on modules from a configured root

This commit is a first shoot at resolving non-relative and non-absolute path from a configured "root folder" (defaulting to `node_modules`). It covers part of the node.js resolution module described in the "File Modules" section of http://nodejs.org/api/modules.html#modules_folders_as_modules
> Without a leading '/' or './' to indicate a file, the module is either a "core module" or is loaded from a node_modules folder.