Adding support for authorization code grant flow

Using server.js - thank you very much for your example, [gatekeeper][0]!

- adding auth. code flow via server proxy (using and adopting server.js from [gatekeeper][0])
- implementing github acces code grant flow
- implementing stack exchange implicit grant flow
- data views remain to be needed for: windows live, github, stack-exchange
- created new header with logo
- counting version number upwards couple of steps because we forgot to increment in the past..

[0]: https://github.com/prose/gatekeeper