Remove final references to json_pure

Gemfile

@@ -1,6 +1,6 @@
 source 'https://rubygems.org'
 
-gemspec name: 'json'
+gemspec
 
 group :development do
   gem "ruby_memcheck" if RUBY_PLATFORM =~ /linux/i

README-json-jruby.md

@@ -3,7 +3,6 @@ JSON-JRuby
 
 JSON-JRuby is a port of Florian Frank's native
 [`json` library](http://json.rubyforge.org/) to JRuby.
-It aims to be a perfect drop-in replacement for `json_pure`.
 
 
 Development version

README.md

@@ -21,10 +21,6 @@ endpoint.
 
 ## Installation
 
-It's recommended to use the extension variant of JSON, because it's faster than
-the pure ruby variant. If you cannot build it on your system, you can settle
-for the latter.
-
 Install the gem and add to the application's Gemfile by executing:
 
     $ bundle add json
@@ -33,12 +29,6 @@ If bundler is not being used to manage dependencies, install the gem by executin
 
     $ gem install json
 
-
-There is also a pure ruby json only variant of the gem, that can be installed
-with:
-
-    $ gem install json_pure
-
 ## Usage
 
 To use JSON you can
@@ -47,20 +37,6 @@ To use JSON you can
 require 'json'
 ```
 
-to load the installed variant (either the extension `'json'` or the pure
-variant `'json_pure'`). If you have installed the extension variant, you can
-pick either the extension variant or the pure variant by typing
-
-```ruby
-require 'json/ext'
-```
-
-or
-
-```ruby
-require 'json/pure'
-```
-
 Now you can parse a JSON document into a ruby data structure by calling
 
 ```ruby

Rakefile

@@ -284,13 +284,11 @@ else
   desc "Create the gem packages"
   task :package do
     sh "gem build json.gemspec"
-    sh "gem build json_pure.gemspec"
     mkdir_p 'pkg'
     mv "json-#{PKG_VERSION}.gem", 'pkg'
-    mv "json_pure-#{PKG_VERSION}.gem", 'pkg'
   end
 
-  desc "Build all gems and archives for a new release of json and json_pure."
+  desc "Build all gems and archives for a new release of json"
   task :build => [ :clean, :package ]
 
   task :release => :build