[Gemfile] Use Xcodeproj refactor branch.

Gemfile

@@ -3,7 +3,7 @@ source "http://rubygems.org"
 gemspec
 
 group :development do
-  gem "xcodeproj", :git => "git://github.com/CocoaPods/Xcodeproj.git"
+  gem "xcodeproj", :git => "git://github.com/CocoaPods/Xcodeproj.git", :branch => "refactor"
   gem "mocha", "~> 0.11.4"
   gem "bacon"
   gem "mocha-on-bacon"

Gemfile.lock

 GIT
   remote: git://github.com/CocoaPods/Xcodeproj.git
-  revision: da9a356535ec7e97c11f2d5648e2f154165c1a19
+  revision: 280a500ed5ee5a5f6bb4e3c5edcfef0240fa427b
+  branch: refactor
   specs:
     xcodeproj (0.3.5)
       activesupport (~> 3.2.6)