Unsafe record handling

[pholica]

I just looked on some code in ThinBkrHandler and found that it changes record that is passed to it. That's perfectly ok, but there is only one record instance passed to all handlers:
https://github.com/tlamer/teres/blob/master/teres/__init__.py#L329
Changing it in one handler influences others, which is not ok. Every handler should have it's own copy of record.

[AloisMahdal]

+1, although there are more issues (handler leaks, race conditons..) that could perhaps benefit from redesigning Record altogether.