add test for simple sinatra/rack app mounting

features/mount_rack.feature

@@ -0,0 +1,8 @@
+Feature: Support Rack apps mounted using map
+
+  Scenario: Mounted Rack App at /sinatra
+    Given the Server is running at "sinatra-app"
+    When I go to "/"
+    Then I should see "Hello World (Middleman)"
+    When I go to "/sinatra/"
+    Then I should see "Hello World (Sinatra)"

fixtures/sinatra-app/config.rb

@@ -0,0 +1,11 @@
+require "sinatra"
+
+class MySinatra < Sinatra::Base
+  get "/" do
+    "Hello World (Sinatra)"
+  end
+end
+
+map "/sinatra" do
+  run MySinatra
+end

fixtures/sinatra-app/source/index.html.erb

@@ -0,0 +1,5 @@
+---
+layout: false
+---
+
+Hello World (Middleman)

middleman.gemspec

@@ -43,6 +43,7 @@ Gem::Specification.new do |s|
   # Development and test
   s.add_development_dependency("slim")
   s.add_development_dependency("rdiscount")
+  s.add_development_dependency("sinatra")
   s.add_development_dependency("coffee-filter", ["~> 0.1.1"])
   s.add_development_dependency("liquid", ["~> 2.2.0"])
   s.add_development_dependency("cucumber", ["~> 1.1.0"])