Update node.d.ts

Verify and Signer are WritableStreams as per:

https://nodejs.org/docs/v0.10.0/api/crypto.html#crypto_class_verify
https://nodejs.org/docs/v0.10.0/api/crypto.html#crypto_class_sign

node/node.d.ts

@@ -1622,12 +1622,12 @@ declare module "crypto" {
         setAutoPadding(auto_padding: boolean): void;
     }
     export function createSign(algorithm: string): Signer;
-    interface Signer {
+    interface Signer extends NodeJS.WritableStream {
         update(data: any): void;
         sign(private_key: string, output_format: string): string;
     }
     export function createVerify(algorith: string): Verify;
-    interface Verify {
+    interface Verify extends NodeJS.WritableStream {
         update(data: any): void;
         verify(object: string, signature: string, signature_format?: string): boolean;
     }