Migration to Express 4.x

Please see the Express documentation for details.

connect-mongo NPM package is currently broken with Express 4.x. Use
this fix in the meantime:
https://github.com/kcbanner/connect-mongo/issues/103#issuecomment-400800
50 .
Fixed locals.cache when NODE_ENV==='production'
Merge branch 'pr/18' into 0.3.0

Conflicts:
	app/routes/core.server.routes.js
	config/express.js
	package.json