Migration to Q.js

Tule is currently using when.js to handle promises. After trying Q.js, that brings really useful functions to promisify node functions, it would be great to use it to make the development easier.

All the when.js references must be replaced by Q ones, trying to refactor at the same time to make unnecessary operations.

After that, when.js dependency should be removed from package.json.

Start by locating all when.js references in the project and reviewing package.json, then trace the promise operations that need to be migrated. Done means the references use Q.js, unnecessary operations have been refactored, and the when.js dependency has been removed from package.json.

Written by the indexing model from the issue text.