Update README to reflect swagger-blocks v3 changes

[PhilippeChab]

Please update the README to reflect #120 changes. Documentation would also be appreciated.

[Evilbits]

Any updates on this? It's possible to get far from following the v3.0 specs but there's still multiple use cases missing and not documented.

[abineetds]

Any update on this? Really struggling to use this without documentation