Typescript missing boolean definition

[neviaumi]

I am new of Typescript and would like using causal for helping generate fake data.

I notice that https://github.com/boo1ean/casual/blob/master/index.d.ts is missing definition of 'boolean' so that I can't invoke casual.boolean in typescript.

I have create monkey patch for fix that issue

`
import * as casual from "casual";

declare interface CasualMonkeyPatch {
boolean: boolean;
}
declare const casualPatch: casual & CasualMonkeyPatch;

export = casualPatch;
`

Hopefully it can merge into master branch index.d.ts .
Also it much much better register that in Typescript official definition repo