Update tutorial.md
Update tutorial.md

Summary:
Fixed typos
Closes https://github.com/facebook/wangle/pull/39

Reviewed By: yfeldblum

Differential Revision: D3308111

Pulled By: elliottneilclark

fbshipit-source-id: f724cba51d9c02a60fdb45c75e8177fd41f05199

facebook/wangle,facebook/wangle,facebook/wangle