Remove V8 runtime since it's not an officially supported interpreter

lib/execjs/runtimes.rb

@@ -4,14 +4,6 @@ module ExecJS
 
     RubyRhino = RubyRhinoRuntime.new
 
-    V8 = ExternalRuntime.new(
-      :name        => "V8",
-      :command     => "v8",
-      :test_args   => "--help",
-      :test_match  => /--crankshaft/,
-      :runner_path => ExecJS.root + "/support/basic_runner.js"
-    )
-
     Node = ExternalRuntime.new(
       :name        => "Node.js (V8)",
       :command     => ["nodejs", "node"],
@@ -46,7 +38,6 @@ module ExecJS
       @runtimes ||= [
         RubyRacer,
         RubyRhino,
-        V8,
         Node,
         JavaScriptCore,
         Spidermonkey,

readme.md

@@ -11,7 +11,6 @@ ExecJS supports these runtimes:
   embedded within MRI Ruby
 * [therubyrhino](https://github.com/cowboyd/therubyrhino) - Mozilla
   Rhino embedded within JRuby
-* [Google V8](http://code.google.com/p/v8/)
 * [Node.js](http://nodejs.org/)
 * Apple JavaScriptCore - Included with Mac OS X
 * [Mozilla Spidermonkey](http://www.mozilla.org/js/spidermonkey/)

test/test_runtimes.rb

@@ -57,7 +57,6 @@ end
 runtimes = [
   "RubyRacer",
   "RubyRhino",
-  "V8",
   "Node",
   "JavaScriptCore",
   "Spidermonkey",