Align the use of the terms "array", "slice" and "vector"

[omasanori]

In Syntaxicon, the type [T, ..n] is referred to as an array and &[T] is done as an slice. A huonw's comment in the FromLiteral RFC also refers to [T, ..n] as an array, &[T] as a slice and Vec<T> as a vector.

However, the tutorial and the reference manual don't conform to it. I think it is a problem.

[nixpulvis]

The documentation at http://doc.rust-lang.org/std/slice/ I find particularly hard to follow.