Add log-request middleware

[kirrg001]

Start with shared middlewares, which every project can use.
Start with: log-request.js middleware.

[kirrg001]

@sebgie has suggested to not generate a new request id if a specific header already exists.
Example: x-request-id
https://devcenter.heroku.com/articles/http-request-id
http://stackoverflow.com/questions/25433258/what-is-the-x-request-id-http-header

By this we can track a request through multiple stages.

[kirrg001]

Request ID header was directly added in Ghost for now (see TryGhost/Ghost#9122). We can port this change over to here as soon as we source out the logging middleware.