Tube -> Tubez

I messed up... I originally named this crate "tube" which is the same name as the primary abstraction (and module) provided by the crate. This makes for a very confusing API given Rust's name-resolution rules (does "tube" refer to the crate? Or does it refer to an imported module? Gotta use "self::tube" to disambiguate...etc).

As such this crate was renamed to "tubez" and all future updates will happen there.