[REQUEST] export `Node` module , please.

[finscn]

When I use typescript , I often do something like this :  (just an example , not in real project)

```

let foo = (node as RegexpLiteral);

let reges = foo.regex ;

```

or 

```

let foo = new Node.Literal();

let bar = new Node.Identifier();

```

But , because  esprima doesn't export Node , So I can't access `Node` module.

Could you export it , and update https://www.npmjs.com/package/@types/esprima  ( https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/esprima ) ?

Then User will use  `esprima.Node` to access it.

Please & Thanks.