Correct an Opal 1.3 compatibility issue

Author: hmdne

Gemfile

@@ -7,7 +7,7 @@ gem 'rack'
 gem 'sinatra'
 gem 'sinatra-websocket'
 # For opal-rspec, a release is needed
-gem 'opal-rspec', github: 'opal/opal-rspec', submodules: true # '>= 0.8.0.alpha1'
+gem 'opal-rspec', github: 'hmdne/opal-rspec', branch: 'opal-1.3', submodules: true # '>= 0.8.0.alpha1'
 gem 'opal-sprockets'
 # Force build of eventmachine on Windows
 gem 'eventmachine', github: 'eventmachine/eventmachine' if RUBY_PLATFORM =~ /mingw/
@@ -16,7 +16,7 @@ gem 'eventmachine', github: 'eventmachine/eventmachine' if RUBY_PLATFORM =~ /min
 # runner
 gem 'selenium-webdriver', require: false
 gem 'rest-client', require: false
-gem 'webdrivers', github: 'hmdne/webdrivers', require: false
+gem 'webdrivers', require: false
 gem 'rexml', require: false
 
 # browser

opal/browser/socket.rb

@@ -4,13 +4,13 @@ module Browser
 # connection.
 #
 # @see https://developer.mozilla.org/en-US/docs/Web/API/WebSocket
-class Socket
+class Socket < IO
   def self.supported?
     Browser.supports? :WebSocket
   end
 
   include Native::Wrapper
-  include IO::Writable
+  include IO::Writable if defined? IO::Writable
   include Event::Target
 
   target {|value|