fix(config): add sauceAgent property to protractor config

Closes #2040

Author: Sergii Naumov

docs/referenceConf.js

@@ -51,6 +51,9 @@ exports.config = {
   // The tests will be run remotely using Sauce Labs.
   sauceUser: null,
   sauceKey: null,
+  // Use sauceAgent if you need customize agent for https connection to
+  // saucelabs.com (i.e. your computer behind corporate proxy)
+  sauceAgent: null,
   // Use sauceSeleniumAddress if you need to customize the URL Protractor
   // uses to connect to sauce labs (for example, if you are tunneling selenium
   // traffic through a sauce connect tunnel). Default is

lib/driverProviders/sauce.js

@@ -56,7 +56,8 @@ SauceDriverProvider.prototype.setupEnv = function() {
   var deferred = q.defer();
   this.sauceServer_ = new SauceLabs({
     username: this.config_.sauceUser,
-    password: this.config_.sauceKey
+    password: this.config_.sauceKey,
+    agent: this.config_.sauceAgent
   });
   this.config_.capabilities.username = this.config_.sauceUser;
   this.config_.capabilities.accessKey = this.config_.sauceKey;