flags for skipping route generation for both action/slice

[kyleplump]

closes #196

i tried to mirror the existing implementation of the other flags, even if we ended up with goofy functions like Generators::App::Action#generate_route?

lmk if you'd like to see any changes, thanks!

[timriley]

The changes here look great, @kyleplump! ❤️ Could you please include one test case for the action + slice generators for when skip_route is passed? After that I think we can get this in!

[kyleplump]

thanks @timriley! i've included the tests for your review. lmk if this works

[timriley]

Thanks @kyleplump!