dave hates jokes :wink:
hello_world.rs -> main.rs
Remove much of the modules section.

This part can get _really_ confusing, and we want to make sure that
people succeed in the guide. I plan on making a module guide in the
future to replace the information here.
remove rich hickey love
don't say 'semantic'
auto merge of #17155 : steveklabnik/rust/dherman_fixes, r=brson

Fixing more suggestions from @dherman . I made them individual commits in case we want to discuss any of them further.