support falsy value for httpAgent and httpsAgent options

Author: felicienfrancois

lib/proxy.js

@@ -49,8 +49,8 @@ Proxy.prototype.listen = function(options, callback) {
   this.httpPort = options.port || 8080;
   this.timeout = options.timeout || 0;
   this.keepAlive = !!options.keepAlive;
-  this.httpAgent = options.httpAgent || new http.Agent({ keepAlive: this.keepAlive });
-  this.httpsAgent = options.httpsAgent || new https.Agent({ keepAlive: this.keepAlive });
+  this.httpAgent = typeof(options.httpAgent) !== "undefined" ? options.httpAgent : new http.Agent({ keepAlive: this.keepAlive });
+  this.httpsAgent = typeof(options.httpsAgent) !== "undefined" ? options.httpsAgent : new https.Agent({ keepAlive: this.keepAlive });
   this.forceSNI = !!options.forceSNI;
   if (this.forceSNI && !this.silent) {
     console.log('SNI enabled. Clients not supporting SNI may fail');