master: updated pod spec

Material.podspec

 Pod::Spec.new do |s|
   s.name = 'Material'
-  s.version = '2.4.17'
+  s.version = '2.4.18'
   s.license = 'BSD-3-Clause'
   s.summary = 'An animation and graphics framework for Material Design in Swift.'
   s.homepage = 'http://materialswift.com'
@@ -8,7 +8,8 @@ Pod::Spec.new do |s|
   s.authors = { 'CosmicMind, Inc.' => 'support@cosmicmind.com' }
   s.source = { :git => 'https://github.com/CosmicMind/Material.git', :tag => s.version }
   s.platform = :ios, '8.0'
-  
+  s.platform = :osx, '10.12'
+
   s.default_subspec = 'Core'
 
   s.subspec 'Core' do |s|