update to support xcode 10 + swift 4

HideShowPasswordTextField.podspec

@@ -1,14 +1,14 @@
 Pod::Spec.new do |spec|
   spec.name = 'HideShowPasswordTextField'
-  spec.version = '0.2'
+  spec.version = '0.3'
   spec.summary = 'Password visibility toggle text field'
   spec.description = 'An easy to use UITextField subclass that adds a visibility toggle and an optional validation checkmark'
   spec.homepage = 'https://github.com/Guidebook/HideShowPasswordTextField'
   spec.license = { type: 'MIT', file: 'LICENSE' }
   spec.source = { git: 'https://github.com/Guidebook/HideShowPasswordTextField.git', tag: "v#{spec.version}" }
   spec.author = { 'Guidebook' => 'developers@guidebook.com', 'Pete Lada' => 'peter@guidebook.com', 'Mike Sprague' => 'mike@guidebook.com', 'Pete Andersen' => 'pandersen@guidebook.com' }
 
-  spec.platform = :ios, '8.0'
+  spec.platform = :ios, '9.0'
   spec.frameworks = 'UIKit'
   spec.source_files = 'HideShowPasswordTextField/*.{h,m,swift}'
   spec.resources = ['HideShowPasswordTextField/*.{png,xib}']