Return the viewable size of the Table as @tuple (x,y)

def size(self):
        """Return the viewable size of the Table as @tuple (x,y)"""
        width = max(
            map(lambda x: x.size()[0], self.sections.itervalues()))

        height = sum(
            map(lambda x: x.size()[1], self.sections.itervalues()))

        return width, height