Pass the class to configure blocks

This allows for the following idiom in top-level apps:

  configure do |app|
    set :foo, app.root + '/foo'
  end

lib/sinatra/base.rb

@@ -811,7 +811,7 @@ module Sinatra
       # Set configuration options for Sinatra and/or the app.
       # Allows scoping of settings for certain environments.
       def configure(*envs, &block)
-        yield if envs.empty? || envs.include?(environment.to_sym)
+        yield self if envs.empty? || envs.include?(environment.to_sym)
       end
 
       # Use the specified Rack middleware

test/base_test.rb

@@ -37,6 +37,18 @@ class BaseTest < Test::Unit::TestCase
         assert_equal 'Foo: ', response.body
       end
     end
+
+    it "passes the subclass to configure blocks" do
+      ref = nil
+      TestApp.configure { |app| ref = app }
+      assert_equal TestApp, ref
+    end
+
+    it "allows the configure block arg to be omitted and does not change context" do
+      context = nil
+      TestApp.configure { context = self }
+      assert_equal self, context
+    end
   end
 
   describe "Sinatra::Base as Rack middleware" do