Fix a couple documentation typos

CryptoSwift/AES.swift

@@ -134,7 +134,7 @@ public class AES {
     }
 
     /**
-    Encrypt message. If padding is necessary, then PKCS7 padding is addedd and need to be removed after decryption.
+    Encrypt message. If padding is necessary, then PKCS7 padding is added and needs to be removed after decryption.
     
     :param: message Plaintext data