Fix wallet write to support windows

lib/wallet.py

@@ -135,15 +135,18 @@ class WalletStorage(object):
 
     def write(self):
         assert not threading.currentThread().isDaemon()
+        temp_path = self.path + '.tmp'
         s = json.dumps(self.data, indent=4, sort_keys=True)
-        with open(self.path + '.tmp', "w") as f:
+        with open(temp_path, "w") as f:
             f.write(s)
-        os.rename(self.path + '.tmp', self.path)
+        os.remove(self.path)
+        os.rename(temp_path, self.path)
         if 'ANDROID_DATA' not in os.environ:
             import stat
             os.chmod(self.path,stat.S_IREAD | stat.S_IWRITE)
 
 
+
 class Abstract_Wallet(object):
     """
     Wallet classes are created to handle various address generation methods.