Fix BABYSTEPPING, add it to Travis test

.travis.yml

   #- opt_enable MAKRPANEL
   #- build_marlin
   #
-  # REPRAP_DISCOUNT_SMART_CONTROLLER
+  # REPRAP_DISCOUNT_SMART_CONTROLLER, SDSUPPORT, and BABYSTEPPING
   #
   - restore_configs
-  - opt_enable REPRAP_DISCOUNT_SMART_CONTROLLER SDSUPPORT
+  - opt_enable REPRAP_DISCOUNT_SMART_CONTROLLER SDSUPPORT BABYSTEPPING
   - build_marlin
   #
   # G3D_PANEL

Marlin/temperature.cpp

       int curTodo = babystepsTodo[axis]; //get rid of volatile for performance
 
       if (curTodo > 0) {
-        babystep(axis,/*fwd*/true);
+        stepper.babystep(axis,/*fwd*/true);
         babystepsTodo[axis]--; //fewer to do next time
       }
       else if (curTodo < 0) {
-        babystep(axis,/*fwd*/false);
+        stepper.babystep(axis,/*fwd*/false);
         babystepsTodo[axis]++; //fewer to do next time
       }
     }