nodes: fix off-by-one error in hex32, hex64 value types

thanks to @nbareil for reporting the issue in #38.
closes #38.

Author: williballenthin

Evtx/Nodes.py

@@ -1469,7 +1469,7 @@ def tag_length(self):
     def string(self):
         ret = "0x"
         b = self.hex()[::-1]
-        for i in range(len(b) - 1):
+        for i in range(len(b)):
             ret += '{:02x}'.format(six.indexbytes(b, i))
         return ret
 
@@ -1489,7 +1489,7 @@ def tag_length(self):
     def string(self):
         ret = "0x"
         b = self.hex()[::-1]
-        for i in range(len(b) - 1):
+        for i in range(len(b)):
             ret += '{:02x}'.format(six.indexbytes(b, i))
         return ret