Using the new way of starting a custom browser

mediawiki_selenium Ruby gem is now able to start local and remote browsers with
optional browser setup.

Paired with Kartik Mistry.

Bug: 62512
Change-Id: I61e5b688711b1976e8df8be94972fe35f6eeb9aa

tests/browser/features/accept_language.feature

@@ -1,4 +1,4 @@
-@custom-browser @phantomjs-bug @sandbox.translatewiki.net
+@custom-browser @sandbox.translatewiki.net
 Feature: Accept-Language
 
   Scenario Outline: Accept-Language

tests/browser/features/step_definitions/accept_language_steps.rb

@@ -1,5 +1,5 @@
 Given(/^that my browser's accept language is (.+)$/) do |language|
-  @browser = browser(environment, test_name(@scenario), language)
+  @browser = browser(test_name(@scenario), {language: language})
   $session_id = @browser.driver.instance_variable_get(:@bridge).session_id
 end