Added tests for mixed str/unicode logging
Added tests for mixed str/unicode logging

Not all of them currently pass

RazerM/logbook,pombredanne/logbook,omergertel/logbook,omergertel/logbook,alonho/logbook,omergertel/logbook,dommert/logbook,DasIch/logbook,Rafiot/logbook,DasIch/logbook,fayazkhan/logbook,DasIch/logbook,alonho/logbook,Rafiot/logbook,FintanH/logbook,alonho/logbook,mitsuhiko/logbook,fayazkhan/logbook,Rafiot/logbook