Commit an arbitrary (picklable) object to the log

def log(self, obj):
        '''
        Commit an arbitrary (picklable) object to the log
        '''
        entries = self.get()
        entries.append(obj)
        # Only log the last |n| entries if set
        if self._size > 0:
            entries = entries[-self._size:]
        self._write_entries(entries)