Clarification of Slice, Vector and Array

Especially in the tutorial beginners should not be confused with
wrong terminology. It helps to know the right names for things
when you want to find something in the documentation.

Author: moonglum

src/doc/tutorial.md

@@ -2385,7 +2385,7 @@ fn print_all<T: Printable>(printable_things: ~[T]) {
 Declaring `T` as conforming to the `Printable` trait (as we earlier
 did with `Clone`) makes it possible to call methods from that trait
 on values of type `T` inside the function. It will also cause a
-compile-time error when anyone tries to call `print_all` on an array
+compile-time error when anyone tries to call `print_all` on a vector
 whose element type does not have a `Printable` implementation.
 
 Type parameters can have multiple bounds by separating them with `+`,
@@ -2428,9 +2428,9 @@ fn draw_all<T: Drawable>(shapes: ~[T]) {
 # draw_all(~[c]);
 ~~~~
 
-You can call that on an array of circles, or an array of rectangles
+You can call that on a vector of circles, or a vector of rectangles
 (assuming those have suitable `Drawable` traits defined), but not on
-an array containing both circles and rectangles. When such behavior is
+a vector containing both circles and rectangles. When such behavior is
 needed, a trait name can alternately be used as a type, called
 an _object_.