created global app view

- the global app view handles references to UI views
- the router now just updated it regarding current app data
moved 'hangup on signout' event listener to CallView
basic setup of a websocket service
live user list through websockets
removed obsolete comment
sync with master
removed the /users REST endpoint as we now rely on WebSockets
added more code comments
Merge pull request #28 from n1k0/live-user-list

Live user list
fixed UserList view did not check for a collection on render
user list is now only retrieved using websockets

- removed users list ws message sent on connect
- do not send a users list on signout
- hide users list if any when not signed in
- fixed ws related tests
better decoupling between views and app data
Improve websocket tests
Merge pull request #30 from n1k0/users-list-subscription

User list is now only retrieved using WebSockets
Environment dependent configuration

- express app is configured depending on the current environment, which
  is set via the `NODE_ENV` environment variable
- env configuration is stored in a JSON file per env: `config-dev.json`
  and `config-prod.json`
- an additional `config-local.json` file may be used to override config
  locally (this file is never versionned)
- a new GET /config.json has been added which serves the configuration
  as JSON depending on the current environment used by the server
- the frontend app consumes this object for configuring itself
- added Make rules for running server in dev mode
- updated README
updated env names to match expressjs conventions
moved JSON config files to a new config/ dir
updated tests
Merge pull request #32 from n1k0/app-env-config

Environment dependent configuration
fixed ws url configuration (refs #32)