add agent parameter

request/request-tests.ts

@@ -92,6 +92,7 @@ var options: request.Options = {
 	qs: obj,
 	json: value,
 	multipart: value,
+    agent: new http.Agent(),  
 	agentOptions: value,
 	agentClass: value,
 	forever: value,

request/request.d.ts

@@ -86,6 +86,7 @@ declare module 'request' {
 			qs?: any;
 			json?: any;
 			multipart?: RequestPart[] | Multipart;
+            agent?: http.Agent;
 			agentOptions?: any;
 			agentClass?: any;
 			forever?: any;