Add Gemfile for test dependencies

Closes #391

Author: kim3er

Gemfile

@@ -0,0 +1,4 @@
+source 'http://rubygems.org'
+
+gem 'sinatra'
+gem 'json'

Gemfile.lock

@@ -0,0 +1,19 @@
+GEM
+  remote: http://rubygems.org/
+  specs:
+    json (1.8.1)
+    rack (1.5.2)
+    rack-protection (1.5.3)
+      rack
+    sinatra (1.4.5)
+      rack (~> 1.4)
+      rack-protection (~> 1.4)
+      tilt (~> 1.3, >= 1.3.4)
+    tilt (1.4.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  json
+  sinatra

README.md

@@ -306,8 +306,9 @@ $ cd jquery-pjax/
 To run the test suite locally, start up the Sinatra test application.
 
 ```
-$ ruby test/app.rb
-== Sinatra/1.3.2 has taken the stage on 4567 for development with backup from WEBrick
+$ bundle install
+$ bundle exec ruby test/app.rb
+== Sinatra/1.4.5 has taken the stage on 4567 for development with backup from WEBrick
 
 $ open http://localhost:4567/
 ```