Update podspec

Author: ra1028

DiffableDataSources.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |spec|
   spec.name = 'DiffableDataSources'
-  spec.version  = '0.2.0'
+  spec.version  = '0.3.0'
   spec.author = { 'ra1028' => '[email protected]' }
   spec.homepage = 'https://github.com/ra1028/DiffableDataSources'
   spec.documentation_url = 'https://ra1028.github.io/DiffableDataSources'