add mongo auth support, and copy a md5 lib to 3rd

lualib/md5.lua

@@ -0,0 +1,18 @@
+----------------------------------------------------------------------------
+-- Modify version from https://github.com/keplerproject/md5
+----------------------------------------------------------------------------
+
+local core = require "md5.core"
+
+----------------------------------------------------------------------------
+-- @param k String with original message.
+-- @return String with the md5 hash value converted to hexadecimal digits
+
+function core.sumhexa (k)
+	k = core.sum(k)
+	return (string.gsub(k, ".", function (c)
+		   return string.format("%02x", string.byte(c))
+		 end))
+end
+
+return core