fix view orders and crossfade strategy

Hero.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = "Hero"
-  s.version          = "0.3.0"
+  s.version          = "0.3.1"
   s.summary          = "Elegant transition library for iOS"
 
   s.description      = <<-DESC

Sources/Info.plist

@@ -15,7 +15,7 @@
 	<key>CFBundlePackageType</key>
 	<string>FMWK</string>
 	<key>CFBundleShortVersionString</key>
-	<string>0.3.0</string>
+	<string>0.3.1</string>
 	<key>CFBundleVersion</key>
 	<string>$(CURRENT_PROJECT_VERSION)</string>
 	<key>NSPrincipalClass</key>

Sources/MatchPreprocessor.swift

@@ -40,8 +40,8 @@ class MatchPreprocessor: BasePreprocessor {
       fvState.spring = tvState.spring
 
       tvState.opacity = 0
-      if !fv.isOpaque || !tv.isOpaque {
-        // cross fade if fromView is not opaque or if toView is transparent
+      if !fv.isOpaque || fv.alpha < 1 || !tv.isOpaque || tv.alpha < 1 {
+        // cross fade if from/toViews are not opaque
         fvState.opacity = 0
       } else {
         // no cross fade in this case, fromView is always displayed during the transition.

Sources/UIKit+Hero.swift

@@ -105,13 +105,7 @@ public extension UIView {
   }
 
   internal var flattenedViewHierarchy: [UIView] {
-    var flattened: [UIView] = [self]
-    var index = 0
-    while index < flattened.count {
-      flattened.append(contentsOf: flattened[index].subviews)
-      index += 1
-    }
-    return flattened
+    return [self] + subviews.flatMap{ $0.flattenedViewHierarchy }
   }
 
   /// Used for .overFullScreen presentation