switch back to Podfile syntax for cocoa pods 0.37

Podfile

@@ -17,7 +17,7 @@ pod 'box-ios-sdk-v2', :git => 'git://github.com/carolanitz/box-ios-sdk-v2.git',
 
 end
 post_install do |installer_representation|
-  installer_representation.pods_project.build_configurations.each do |config|
+  installer_representation.project.build_configurations.each do |config|
             config.build_settings['SKIP_INSTALL'] = 'YES'
             config.build_settings['VALID_ARCHS'] = 'armv7 armv7s arm64'
             config.build_settings['ARCHS'] = 'armv7 armv7s arm64'