Add typings for module usage

usage/usage.d.ts

@@ -0,0 +1,28 @@
+// Type definitions for usage
+// Project: https://github.com/arunoda/node-usage
+// Definitions by: Pascal Vomhoff <https://github.com/pvomhoff>
+// Definitions: https://github.com/borisyankov/DefinitelyTyped
+
+declare module "usage" {
+
+  export interface ResultObject {
+    memory:number;
+    memoryInfo: {
+      rss:number;
+      vsize:number;
+    }
+    cpu:number;
+  }
+
+  export interface Options {
+    keepHistory:boolean;
+  }
+
+  export function lookup(pid:number, callback:(err:Error, result:ResultObject) => void);
+  export function lookup(pid:number, options:Options, callback:(err:Error, result:ResultObject) => void);
+
+  //Only availible on linux
+  export function clearHistory(pid?:number);
+
+
+}