fix get_data_ranges() for Mayavi 4.6.2
fix get_data_ranges() for Mayavi 4.6.2

sfepy/sfepy,rc/sfepy,BubuLK/sfepy,BubuLK/sfepy,BubuLK/sfepy,rc/sfepy,vlukes/sfepy,sfepy/sfepy,sfepy/sfepy,vlukes/sfepy,rc/sfepy,vlukes/sfepy