fix: pass contentState through to decorators

[echenley]

Adds support for DraftJS v0.10.0, which expects contentState to be passed in to each decorator.

See https://facebook.github.io/draft-js/docs/v0-10-api-migration.html and https://github.com/facebook/draft-js/blob/master/src/model/decorators/DraftDecoratorType.js.

[sashless]

~~Can this be merged into master please? :+1: Hm unfortunately this doenst work for me. Does it still work for you @echenley ? decorator.getDecorations is not a function~~

Well okay, the example in the readme is just not complete. I checked tests and it needs to be new MultiDecorator([new Draft.CompositeDecorator([..])]). Doing that it works for me :+1:

[i11v]

@SamyPesse, merge this please

[juliankrispel]

@SamyPesse please merge matey <3

[christophepas]

@SamyPesse please merge ;)