Added an example of manually scheduling an RVar.
Added an example of manually scheduling an RVar.


Former-commit-id: 35e2dcf8ade7c8c9044531025232b65f01241c69
darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide