use helmet module to more secure application

Helmet module is the middleware to add security headers for Application.
I think these headers is so important for security that we should also use in MEAN.js.

We need to install the latest one from github currently because it looks old on the npm site.
The old one is not working on my local MEAN.js stack.
keep enable Cache-Control

helmet.defaults() disabeles Cache-Control. I guess it's controversial to disable it.
Add envvars for deploying to cloud providers
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 .
Merge branch 'pr/18' into 0.2.3
Merge branch 'pr/14' into 0.2.3
Merge branch 'pr/15' into 0.2.3
Fixed locals.cache when NODE_ENV==='production'
merge upstream 0.2.3
workaround for express 4 connectMongo session bug
0.3RC

Express 4 Support
New naming convention
Glob patterns
CSS Linting
Uglify
CSS Min
Environmental Asset Management
DI Menu System
Merge branch 'pr/18' into 0.3.0

Conflicts:
	app/routes/core.server.routes.js
	config/express.js
	package.json
Comment Fixes
More Naming Fixes, articles cleanup
Added role based middleware authorisation
add missing dependencies

The packages connect-mongo and connect-flash are missing in the package.json
Merge branch 'pr/29' into 0.3.0
Fix intdentation
Fixing Articles Issues
Merge branch 'pr/24' into 0.3.0

Conflicts:
	config/env/all.js
	config/express.js
	package.json