* fill in stub for helmet lesson on noSniff()
* fill in stub for helmet lesson ieNoOpen()
* fill in helmet hsts() stub
* fill in stub for helmetjs lesson-DNS prefetching
* fill in stub for helmet lesson on noCache()
* fill in stub for helmetjs lesson on XSS
* fill in stub for helmet lesson 'parent'
* fill in stub for lesson on bcrypt
* fix type `is` to `it` on line 11
* fill in stub for bcrypt hash lesson
* fill in stub for bcrypt hash sync
* fill stub for helmet lessons overview
* fix spacing
* fix typo