Upgrade to express 4
Add language selector to the docs&primary-nav

Add language selector,and change twitter to weibo because we cann’t
visit twitter at china :(
This file should be in the last commit
Remove console.log in view function

There was a console.log in view function to show the
req.session.currentLanguage for debug,not need it anymore.
removed express 3.x related comments
updated express 4.x related packages
Merge branch 'master' of github.com:keystonejs/keystone into express4r3dm

Conflicts:
	lib/core/start.js
	package.json
fixed package.json merge
changed convention for session storage. We now pass in sessionStore which derives from the new express-session module
updated docs script to express 4 conventions
removed warnings raised by express 4
fixed typo
fix for resave on session
Merge pull request #767 from r3dm/express4r3dm

Express4r3dm
Updating session options initialisation for express 4
fix express-session warning by passing cookie secret into it. We now pass the cookie session into express-session as well as cookie-parser modules
Merge pull request #770 from r3dm/express4

fix express-session warning by passing cookie secret into it. We now pas...
Merge branch 'master' into express4

Conflicts:
	docs/docs.js
fix s3File fieldtype bug. Change 'file.type' to 'file.mimetype'
Merge pull request #780 from r3dm/fix-s3

fix s3File fieldtype bug. Change 'file.type' to 'file.mimetype'