Fix podspec

Author: a2

MessagePack.swift.podspec

@@ -10,5 +10,6 @@ Pod::Spec.new do |s|
   s.watchos.deployment_target = '2.0'
   s.tvos.deployment_target = '9.0'
   s.source       = { :git => 'https://github.com/a2/MessagePack.swift.git', :tag => s.version.to_s }
-  s.source_files = 'Sources/*.swift'
+  s.source_files = 'Sources/MessagePack/*.swift'
+  s.module_name  = 'MessagePack'
 end