security: Change IdentityStorage.getCertificate to return Certificate instead of Data.
diff --git a/ndn-cpp/security/identity/memory-identity-storage.cpp b/ndn-cpp/security/identity/memory-identity-storage.cpp
index a70c339..a7acf84 100644
--- a/ndn-cpp/security/identity/memory-identity-storage.cpp
+++ b/ndn-cpp/security/identity/memory-identity-storage.cpp
@@ -118,7 +118,7 @@
 #endif
 }
 
-ptr_lib::shared_ptr<Data> 
+ptr_lib::shared_ptr<Certificate> 
 MemoryIdentityStorage::getCertificate(const Name &certificateName, bool allowAny)
 {
 #if 1