[Gemfile] Use custom Core branch

Gemfile

@@ -15,7 +15,7 @@ gem 'json', '1.7.7'
 
 group :development do
   cp_gem 'claide',               'CLAide'
-  cp_gem 'cocoapods-core',       'Core'
+  cp_gem 'cocoapods-core',       'Core',                'swift'
   cp_gem 'cocoapods-downloader', 'cocoapods-downloader'
   cp_gem 'cocoapods-plugins',    'cocoapods-plugins'
   cp_gem 'cocoapods-trunk',      'cocoapods-trunk'

Gemfile.lock

@@ -7,8 +7,8 @@ GIT
 
 GIT
   remote: https://github.com/CocoaPods/Core.git
-  revision: c9c91c5296067ebf5af122ed87580e9f0479b47c
-  branch: master
+  revision: 8bfbc96858947f4db6dd1f4a3ea085b446ad35d3
+  branch: swift
   specs:
     cocoapods-core (0.35.0)
       activesupport (>= 3.2.15)