Deprecate Johnson

Gemfile

@@ -4,9 +4,6 @@ gemspec
 
 group :test do
   gem 'json'
-  # see https://github.com/jbarnette/johnson/issues/21
-  gem 'johnson',      :platform => :mri_18
-  # disabled for rbx, because of https://github.com/cowboyd/therubyracer/issues/157
   gem 'therubyracer', :platform => :mri
   gem 'therubyrhino', ">=1.73.3", :platform => :jruby
 end

README.md

@@ -11,8 +11,6 @@ ExecJS supports these runtimes:
   embedded within Ruby
 * [therubyrhino](https://github.com/cowboyd/therubyrhino) - Mozilla
   Rhino embedded within JRuby
-* [Johnson](https://github.com/jbarnette/johnson) - Mozilla
-  SpiderMonkey embedded within Ruby
 * [Node.js](http://nodejs.org/)
 * Apple JavaScriptCore - Included with Mac OS X
 * [Microsoft Windows Script Host](http://msdn.microsoft.com/en-us/library/9bbdkx3k.aspx) (JScript)

lib/execjs/johnson_runtime.rb

@@ -98,5 +98,9 @@ module ExecJS
     rescue LoadError
       false
     end
+
+    def deprecated?
+      true
+    end
   end
 end