Replacing 'agent' option with 'httpAgent' and 'httpsAgent'

lib/adapters/http.js

@@ -61,13 +61,17 @@ module.exports = function httpAdapter(config) {
       var urlPassword = urlAuth[1] || '';
       auth = urlUsername + ':' + urlPassword;
     }
+
+    var isHttps = parsed.protocol === 'https:';
+    var agent = isHttps ? config.httpsAgent : config.httpAgent;
+
     var options = {
       hostname: parsed.hostname,
       port: parsed.port,
       path: buildURL(parsed.path, config.params, config.paramsSerializer).replace(/^\?/, ''),
       method: config.method,
       headers: headers,
-      agent: config.agent,
+      agent: agent,
       auth: auth
     };
 
@@ -79,12 +83,12 @@ module.exports = function httpAdapter(config) {
 
     var transport;
     if (config.maxRedirects === 0) {
-      transport = parsed.protocol === 'https:' ? https : http;
+      transport = isHttps ? https : http;
     } else {
       if (config.maxRedirects) {
         options.maxRedirects = config.maxRedirects;
       }
-      transport = parsed.protocol === 'https:' ? httpsFollow : httpFollow;
+      transport = isHttps ? httpsFollow : httpFollow;
     }
 
     // Create the request