Add NgModules

[tb]

@dharmeshpipariya first of all thank you for awesome work!

Adding NgModules would be greater, see angular/components#950

[dharmeshpipariya-zz]

@tb we are working on it, we will update soon.

[dharmeshpipariya-zz]

@tb we have added NgModules on all components and published on npm you can refer our latest code on https://github.com/Promact/material2/tree/promact and use from npm on https://www.npmjs.com/package/md2

[tb]

@dharmeshpipariya I find it confusing that md2 package is published from https://github.com/Promact/material2/tree/promact

Why you are not using https://github.com/Promact/md2/tree/master?

I would like to contribute to this project, i.e. help migrate to rc.6 or add some component tests.