updated Material.podspec

Material.podspec

@@ -10,7 +10,7 @@ Pod::Spec.new do |s|
   s.ios.deployment_target = '8.0'
   s.ios.source_files = 'Sources/iOS/**/*.swift'
   s.osx.deployment_target = '10.9'
-  s.osx.source_files = 'Sources/OSX/**/*.swift'
+  s.osx.source_files = 'Sources/macOS/**/*.swift'
   s.requires_arc = true
   s.resource_bundles = {
       'io.cosmicmind.material.icons' => ['Sources/**/*.xcassets'],