Disable availability warnings.

This warning only knows about the new `@available` objc language feature (that matches the Swift one). All the cases it catches are already blocked by other methods, like selector testing, so it's not actually a problem. We can't add `@available` calls until we drop Xcode 8 support so disabling temporarily seems the best solution.

Stripe.podspec

@@ -14,4 +14,5 @@ Pod::Spec.new do |s|
   s.public_header_files            = 'Stripe/PublicHeaders/*.h'
   s.source_files                   = 'Stripe/PublicHeaders/*.h', 'Stripe/*.{h,m}'
   s.ios.resource_bundle            = { 'Stripe' => 'Stripe/Resources/**/*' }
+  s.compiler_flags                 = '-Wno-unguarded-availability'
 end

Stripe/BuildConfigurations/StripeiOS-Shared.xcconfig

@@ -25,7 +25,7 @@ CLANG_WARN_INFINITE_RECURSION = YES
 CLANG_WARN_SUSPICIOUS_MOVE = YES
 CLANG_WARN_ASSIGN_ENUM = YES
 CLANG_WARN_DOCUMENTATION_COMMENTS = YES
-
+CLANG_WARN_UNGUARDED_AVAILABILITY = NO
 
 // Code Signing Identity
 // 

Tests/installation_tests/cocoapods/with_frameworks/Podfile

@@ -1,6 +1,7 @@
 use_frameworks!
 
 target 'CocoapodsTest' do
+	platform :ios, '8.0'
 	use_frameworks!
 	pod 'Stripe', path: '../../../..'
 end