added self.create to the request

With this it is possible to reuse an already set request and therefore
safe some memory and time.

lib/zero/request.rb

@@ -6,9 +6,15 @@ require_relative 'request/server'
 module Zero
   # This class wraps around a rack environment for easier access to all data.
   class Request
+    def self.create(environment)
+      return environment['zero.request'] if environment.has_key?('zero.request')
+      new(environment)
+    end
+
     # create a new request object
     def initialize(env)
       @env = env
+      @env['zero.request'] = self
     end
 
     # get the environment

spec/unit/request/create_spec.rb

@@ -0,0 +1,21 @@
+require 'spec_helper'
+
+describe Zero::Request, '.create' do
+  subject { Zero::Request.new(env) }
+
+  context "with a fresh environment" do
+    let(:env) { EnvGenerator.get('/foo') }
+    it "creates an instance of Zero::Request" do
+      Zero::Request.create(env).should be_an_instance_of(Zero::Request)
+    end
+  end
+
+  context "with an already used environment" do
+    let(:env) { EnvGenerator.get('/foo') }
+    let(:new_env) { subject.env }
+
+    it "returns an already build request" do
+      Zero::Request.create(new_env).should be(subject)
+    end
+  end
+end