Update podspec syntax

GAppAuth.podspec

@@ -1,24 +1,16 @@
-#
-#  Be sure to run `pod spec lint GAppAuth.podspec' to ensure this is a
-#  valid spec and to remove all comments including this before submitting the spec.
-#
-#  To learn more about Podspec attributes see http://docs.cocoapods.org/specification.html
-#  To see working Podspecs in the CocoaPods repo see https://github.com/CocoaPods/Specs/
-#
-
 Pod::Spec.new do |s|
-  s.name         = "GAppAuth"
-  s.version      = "1.2.0"
-  s.summary      = "Convenient Wrapper for AppAuth with Google Services written in Swift 3 (iOS)."
-  s.homepage     = "https://github.com/elsesiy/GAppAuth"
-  s.license      = "BSD-2-Clause"
-  s.author             = "Jonas-Taha El Sesiy"
-  s.social_media_url   = "http://twitter.com/elsesiy"
-  s.source       = { :git => "https://github.com/elsesiy/GAppAuth.git", :tag => s.version }
-  s.source_files  = "Sources/GAppAuth.swift"
-  s.swift_version = "4.0"
+  s.name         = 'GAppAuth'
+  s.version      = '1.2.0'
+  s.summary      = 'Convenient Wrapper for AppAuth with Google Services written in Swift 4 (iOS).'
+  s.homepage     = 'https://github.com/elsesiy/GAppAuth'
+  s.license      = 'BSD-2-Clause'
+  s.author             = 'Jonas-Taha El Sesiy'
+  s.social_media_url   = 'http://twitter.com/elsesiy'
+  s.source       = { :git => 'https://github.com/elsesiy/GAppAuth.git', :tag => s.version }
+  s.source_files  = 'Sources/GAppAuth.swift'
+  s.swift_version = '4.0'
   #s.tvos.deployment_target = '9.0'
   #s.osx.deployment_target = '10.9'
-  s.ios.deployment_target = "8.0"
-  s.dependency "GTMAppAuth", '~> 0.7.0'
+  s.ios.deployment_target = '8.0'
+  s.dependency 'GTMAppAuth', '~> 0.7.0'
 end