Throng improvements

- Relax workers value to be a string or number. The library handles
both, and this value is frequently supplied as an ENV.
- Relax master in config object to be optional

types/throng/index.d.ts

@@ -1,18 +1,21 @@
 // Type definitions for throng 4.0
 // Project: https://github.com/hunterloftis/throng
 // Definitions by: Cyril Schumacher <https://github.com/cyrilschumacher>
+//                 Tate Thurston <https://github.com/tatethurston>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
-declare function throng(options: throng.WorkerCallback | throng.Options | number, startFunction?: throng.WorkerCallback): void;
+declare function throng(startOrOptions: throng.ProcessCallback | throng.Options): void;
+declare function throng(workers: throng.WorkerCount, start: throng.ProcessCallback): void;
 declare namespace throng {
-    type WorkerCallback = (id: number) => void;
+    type WorkerCount = number | string;
+    type ProcessCallback = (id: number) => any;
 
     interface Options {
         grace?: number;
         lifetime?: number;
-        master(): void;
-        start: WorkerCallback;
-        workers: number;
+        master?: ProcessCallback;
+        start: ProcessCallback;
+        workers?: WorkerCount;
     }
 }