Remove the HTTPkit adapter

The HTTPkit project seems not to be maintained:

- the git repository has been removed from GitHub
- there has been no release since 2014

Gemfile

@@ -15,11 +15,6 @@ group :test do
   gem "websocket_parser", "~>1.0"
 end
 
-group :webservers do
-  gem 'http', '~> 0.6.0'
-  gem 'httpkit', :platform => [:mri, :rbx]
-end
-
 group :guard do
   gem 'guard-rspec', '~> 4.7'
   case RbConfig::CONFIG['host_os']

README.md

@@ -20,8 +20,7 @@ are up to you.
   requests, and response codes for you.
 * Provides a base resource with points of extension to let you
   describe what is relevant about your particular resource.
-* Supports WEBrick, Reel, HTTPkit, and a Rack shim. Other host
-  servers are being investigated.
+* Supports WEBrick and a Rack shim. Other host servers are being investigated.
 * Streaming/chunked response bodies are permitted as Enumerables,
   Procs, or Fibers!
 * Unlike the Erlang original, it does real Language negotiation.

documentation/adapters.md

@@ -1,7 +1,7 @@
 ### Adapters
 
-Webmachine includes adapters for [WEBrick][webrick], and
-[HTTPkit][httpkit]. Additionally, the [Rack][rack] adapter lets it
+Webmachine includes an adapter for [WEBrick][webrick].
+Additionally, the [Rack][rack] adapter lets it
 run on any webserver that provides a Rack interface. It also lets it run on
 [Shotgun][shotgun] ([example][shotgun_example]).
 
@@ -24,15 +24,7 @@ For an example of using Webmachine with Rack middleware, see the [Pact Broker][m
 
 See the [Rack Adapter API docs][rack-adapter-api-docs] for more information.
 
-#### A Note about MRI 1.9
-
-The [HTTPkit][httpkit]
-adapter might crash with a `SystemStackError` on MRI 1.9 due to its
-limited fiber stack size. If your application is affected by this, the
-only known solution is to switch to JRuby, Rubinius or MRI 2.0.
-
 [webrick]: http://rubydoc.info/stdlib/webrick
-[httpkit]: https://github.com/lgierth/httpkit
 [rack]: https://github.com/rack/rack
 [shotgun]: https://github.com/rtomayko/shotgun
 [shotgun_example]: https://gist.github.com/4389220

lib/webmachine/adapters.rb

@@ -5,6 +5,5 @@ module Webmachine
   # Contains classes and modules that connect Webmachine to Ruby
   # application servers.
   module Adapters
-    autoload :HTTPkit,  'webmachine/adapters/httpkit'
   end
 end

spec/spec_helper.rb

@@ -1,5 +1,5 @@
 require "bundler/setup"
-Bundler.require :default, :test, :webservers
+Bundler.require :default, :test
 require 'logger'
 
 class NullLogger < Logger