Open Source ABTesting (#3507)

* CI for ABTesting
* README update

FirebaseABTesting.podspec

@@ -0,0 +1,51 @@
+Pod::Spec.new do |s|
+  s.name             = 'FirebaseABTesting'
+  s.version          = '3.1.0'
+  s.summary          = 'Firebase ABTesting for iOS'
+
+  s.description      = <<-DESC
+A/B testing is a Firebase service that lets you run experiments across users of
+your iOS and Android apps. It lets you learn how well one or more changes to
+your app work with a smaller set of users before you roll out changes to all
+users. You can run experiments to find the most effective ways to use
+Firebase Cloud Messaging and Firebase Remote Config in your app.
+                       DESC
+
+  s.homepage         = 'https://firebase.google.com'
+  s.license          = { :type => 'Apache', :file => 'LICENSE' }
+  s.authors          = 'Google, Inc.'
+
+  s.source           = {
+    :git => 'https://github.com/firebase/firebase-ios-sdk.git',
+    :tag => 'ABTesting-' + s.version.to_s
+  }
+  s.social_media_url = 'https://twitter.com/Firebase'
+  s.ios.deployment_target = '8.0'
+  s.osx.deployment_target = '10.11'
+  s.tvos.deployment_target = '10.0'
+
+  s.cocoapods_version = '>= 1.4.0'
+  s.static_framework = true
+  s.prefix_header_file = false
+
+  base_dir = "FirebaseABTesting/Sources/"
+  s.source_files = base_dir + '**/*.[mh]'
+  s.requires_arc = base_dir + '*.m'
+  s.public_header_files = base_dir + 'Public/*.h'
+  s.pod_target_xcconfig = {
+    'GCC_C_LANGUAGE_STANDARD' => 'c99',
+    'GCC_PREPROCESSOR_DEFINITIONS' =>
+      'GPB_USE_PROTOBUF_FRAMEWORK_IMPORTS=1 ' +
+      'FIRABTesting_VERSION=' + String(s.version),
+    'HEADER_SEARCH_PATHS' => '"${PODS_TARGET_SRCROOT}"'
+  }
+  s.dependency 'FirebaseAnalyticsInterop', '~> 1.3'
+  s.dependency 'FirebaseCore', '~> 6.1'
+  s.dependency 'Protobuf', '~> 3.8'
+
+  s.test_spec 'unit' do |unit_tests|
+    unit_tests.source_files = 'FirebaseABTesting/Tests/Unit/*.[mh]'
+    unit_tests.requires_app_host = true
+    unit_tests.dependency 'OCMock'
+  end
+end