Fixing require() vs require_once()

See : https://github.com/tommcfarlin/WordPress-Plugin-Boilerplate/issues/222. I believe this was in favor of doing it "correctly"?
Merge pull request #231 from NikV/patch-1

Fixing require() vs require_once()
Fix code comment typo
Merge pull request #235 from barryceelen/patch-1

Fix code comment typo