Add travis widget, fix documented node dependency
Add travis widget, fix documented node dependency

UCL-ShippingGroup/Windshaft-cartodb,CartoDB/Windshaft-cartodb,UCL-ShippingGroup/Windshaft-cartodb,manueltimita/Windshaft-cartodb,UCL-ShippingGroup/Windshaft-cartodb,CartoDB/Windshaft-cartodb,manueltimita/Windshaft-cartodb,manueltimita/Windshaft-cartodb,CartoDB/Windshaft-cartodb,CartoDB/Windshaft-cartodb