updated swift version in spec

Author: pingwinator

WebLinking.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |spec|
   spec.name = 'WebLinking'
-  spec.version = '2.0.0'
+  spec.version = '2.0.1'
   spec.summary = 'Swift implementation of Web Linking and Link headers (RFC5988)'
   spec.homepage = 'https://github.com/kylef/WebLinking.swift'
   spec.license = { :type => 'MIT', :file => 'LICENSE' }
@@ -13,4 +13,5 @@ Pod::Spec.new do |spec|
   spec.watchos.deployment_target = '2.0'
   spec.tvos.deployment_target = '9.0'
   spec.requires_arc = true
+  spec.swift_version = '4.0'
 end