Optimization bugs fixed.
1. Add some missing properties for some expressions.
2. Add compute_shape() for expressions.
3. Turn on RotateSlice.
Merge branch 'master' into optimization
Add missing properties and functions to LocalWrapper
Add children_order parameters in Map and Reduce.
Iterate over children_order when order must be protected.
Comment
children is a ListExpr now
Merge pull request #99 from fegin/optimization

Optimization bugs fixed