Add Ruby 2.4

Author: route

.circleci/config.yml

@@ -46,5 +46,5 @@ workflows:
       - test:
           matrix:
             parameters:
-              ruby-version: ["2.5", "2.6", "2.7"]
+              ruby-version: ["2.4", "2.5", "2.6", "2.7"]
               gemfile: ["gemfiles/capybara-2.x.gemfile", "gemfiles/capybara-3.x.gemfile", "gemfiles/websocket-driver-6.x.gemfile", "gemfiles/ferrum-master.gemfile"]

.gitignore

@@ -1,3 +1,4 @@
 .byebug_history
 Gemfile.*
 .ruby-version
+save_path_tmp

README.md

@@ -1,6 +1,6 @@
 # Cuprite - Headless Chrome driver for Capybara
 
-[![Build Status](https://circleci.com/gh/rubycdp/cuprite.svg?style=shield)](https://circleci.com/gh/rubycdp/cuprite)
+[![CircleCI](https://circleci.com/gh/rubycdp/cuprite.svg?style=shield)](https://circleci.com/gh/rubycdp/cuprite)
 
 Cuprite is a pure Ruby driver (read as _no_ Selenium/WebDriver/ChromeDriver
 dependency) for [Capybara](https://github.com/teamcapybara/capybara). It allows