Enumerator using generic. Cleaner for .. in .. loop in Swift (#433)

* Enumerator using generic. Cleaner for .. in .. loop in Swift

So 
for childSnapshot in snapshot.children {
you don't need to cast each child. Each cild is already known as DataSnapshot

* Update FIRDataSnapshot.h

* Update FIRMutableData.h

* Update FIRMutableData.m

2 files changed, 2 insertions, 2 deletions

diff --git a/Firebase/Database/Public/FIRDataSnapshot.h b/Firebase/Database/Public/FIRDataSnapshot.h
index c3082df..e465045 100644
--- a/Firebase/Database/Public/FIRDataSnapshot.h
+++ b/Firebase/Database/Public/FIRDataSnapshot.h
@@ -134,7 +134,7 @@ FIR_SWIFT_NAME(DataSnapshot)
  *
  * @return An NSEnumerator of the children.
  */
-@property (strong, readonly, nonatomic) NSEnumerator* children;
+@property (strong, readonly, nonatomic) NSEnumerator<FIRDataSnapshot *>* children;
 
 /**
  * The priority of the data in this FIRDataSnapshot.
diff --git a/Firebase/Database/Public/FIRMutableData.h b/Firebase/Database/Public/FIRMutableData.h
index 5c26024..4e7250a 100644
--- a/Firebase/Database/Public/FIRMutableData.h
+++ b/Firebase/Database/Public/FIRMutableData.h
@@ -116,7 +116,7 @@ FIR_SWIFT_NAME(MutableData)
  * Note that this enumerator operates on an immutable copy of the child list. So, you can modify the instance
  * during iteration, but the new additions will not be visible until you get a new enumerator.
  */
-@property (readonly, nonatomic, strong) NSEnumerator* children;
+@property (readonly, nonatomic, strong) NSEnumerator<FIRMutableData *>* children;
 
 
 /**