feat(ios): adapt build to post bintray world (#309)

Part of https://github.com/ooni/probe/issues/1437

MOBILE/template.podspec

@@ -1,12 +1,12 @@
 Pod::Spec.new do |s|
   s.name = "oonimkall"
   s.version = "@VERSION@"
-  s.summary = "OONI Probe Engine for iOS"
+  s.summary = "OONI Probe Library for iOS"
   s.author = "Simone Basso"
-  s.homepage = "https://github.com/ooni/probe-engine"
+  s.homepage = "https://github.com/ooni/probe-cli"
   s.license = { :type => "BSD" }
   s.source = {
-    :http => "https://dl.bintray.com/ooni/ios/oonimkall-@VERSION@.framework.zip"
+    :http => "https://github.com/ooni/probe-cli/releases/download/@RELEASE@/oonimkall.framework.zip"
   }
   s.platform = :ios, "9.0"
   s.ios.vendored_frameworks = "oonimkall.framework"