add handling for superagent pfx with passphrase

types/superagent/index.d.ts

@@ -4,6 +4,7 @@
 //                 Michael Ledin <https://github.com/mxl>
 //                 Pap Lőrinc <https://github.com/paplorinc>
 //                 Shrey Jain <https://github.com/shreyjain1994>
+//                 Alec Zopf <https://github.com/zopf>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.2
 
@@ -131,7 +132,7 @@ declare namespace request {
         on(name: string, handler: (event: any) => void): this;
         parse(parser: Parser): this;
         part(): this;
-        pfx(cert: Buffer | string): this;
+        pfx(cert: Buffer | string | { pfx: Buffer, passphrase: string }): this;
         pipe(stream: NodeJS.WritableStream, options?: object): stream.Writable;
         query(val: object | string): this;
         redirects(n: number): this;

types/superagent/superagent-tests.ts

@@ -373,6 +373,16 @@ request
     .pfx(pfx)
     .end(callback);
 
+// pfx with passphrase, from: https://github.com/visionmedia/superagent/pull/1230/commits/96af65ffc6256df633f893095d1dc828694bbfbc
+const passpfx = fs.readFileSync('passcert.pfx');
+request
+    .post('/secure')
+    .pfx({
+        pfx: passpfx,
+        passphrase: 'test'
+    })
+    .end(callback);
+
 // ok, from: https://github.com/visionmedia/superagent/commit/34533bbc29833889090847c45a82b0ea81b2f06d
 request
     .get('/404')