Always copy headers to ./Pods instead of using the PRODUCT_NAME, which changes…

Always copy headers to ./Pods instead of using the PRODUCT_NAME, which changes for each Pods target. Fixes #75.

lib/cocoapods/xcodeproj_ext.rb

@@ -15,7 +15,7 @@ module Xcodeproj
     class PBXCopyFilesBuildPhase
       def self.new_pod_dir(project, pod_name, path)
         new(project, nil, {
-          "dstPath" => "$(PRODUCT_NAME)/#{path}",
+          "dstPath" => "Pods/#{path}",
           "name"    => "Copy #{pod_name} Public Headers",
         })
       end

spec/unit/xcodeproj_ext_spec.rb

@@ -27,7 +27,7 @@ describe 'Xcodeproj::Project' do
     phase = @project.targets.first.copy_files_build_phases.new_pod_dir("SomePod", "Path/To/Source")
     find_object({
       'isa' => 'PBXCopyFilesBuildPhase',
-      'dstPath' => '$(PRODUCT_NAME)/Path/To/Source',
+      'dstPath' => 'Pods/Path/To/Source',
       'name' => 'Copy SomePod Public Headers'
     }).should.not == nil
     @project.targets.first.buildPhases.should.include phase