It's Rust convention for method names to be in snake case, so much so
that the compiler emits a warning by default for non-snake-case methods.
Reading something like `HttpResponse::Ok()` leads me to believe that I'm
creating an instance of the `Ok` variant of a `HttpResponse` enum, but
for some reason there's no associated data (which _is_ possible, there's
just no reason to define an enum that way).
There are other cases of #[allow(non_snake_case)] in the actix codebase,
but this commit only addresses the `HttpResponse::XXX()` methods.
lberrymage
fakeshadow
Patrick Tescher
Yuki Okushi
Maxim Vorobjov