Fix error where only the first byte of a trailing UTF-8 character was output

lib/excoder.ex

@@ -2053,7 +2053,7 @@ defmodule ExCoder do
         end
     end
 
-    def decode(<< first :: utf8, rest :: binary >>), do: << first >> <> decode rest
+    def decode(str), do: String.first(str) <> decode String.slice str, 1, String.length str
 
 
     def decode(numeric, :numericmode) when is_number numeric do