Rand: update to work with latest rand version

src/rand.md

@@ -7,16 +7,14 @@ To use the `rand` crate, just do the following in your `Cargo.toml` file.
 
 ```
 [dependencies]
-rand = "0.7.3"
+rand = "0.8.5"
 ```
 
 ## Get a random number
 
 To get a random number, you can simply do the following.
 
 ```rust,editable
-# extern crate rand;
-
 fn main() {
     let i: i32 = rand::random();
     println!("The random i32 is {}", i);
@@ -26,8 +24,6 @@ fn main() {
 The `random()` is smart enough to know the primitive type it is **supposed** to generate. Check out the example below.
 
 ```rust,editable
-# extern crate rand;
-
 fn main() {
     let x: u8 = rand::random();
     println!("The random u8 is {}", x);
@@ -44,16 +40,14 @@ What about generating a random number within a range? For that, you need to
 create a random number generator and call its `gen_range()` function.
 
 ```rust,editable
-# extern crate rand;
-
 use rand::thread_rng;
 use rand::Rng;
 
 fn main() {
     let mut rng = thread_rng();
-    let y: f64 = rng.gen_range(-10.0, 10.0);
+    let y: f64 = rng.gen_range(-10.0..=10.0);
     println!("Number from -10. to 10.: {}", y);
-    println!("Number from 0 to 9: {}", rng.gen_range(0, 10));
+    println!("Number from 0 to 9: {}", rng.gen_range(0..10));
 }
 ```
 
@@ -65,24 +59,20 @@ a new random number generator. It is faster to create the generator once and
 call its `gen()` function repeatedly.
 
 ```rust,editable
-# extern crate rand;
-
 use rand::thread_rng;
 use rand::Rng;
 
 fn main() {
     let mut rng = thread_rng();
     for i in 1..10 {
-        println!("Random number #{}: {}", i, rng.gen_range(0, 100));
+        println!("Random number #{}: {}", i, rng.gen_range(0..=100));
     }
 }
 ```
 
 The generator can quickly fill an array with random integers.
 
 ```rust,editable
-# extern crate rand;
-
 use rand::thread_rng;
 use rand::Rng;
 
@@ -97,8 +87,6 @@ Another neat feature of the generator is that it can generate random numbers
 from a probability distribution.
 
 ```rust,editable
-# extern crate rand;
-
 use rand::thread_rng;
 use rand::Rng;
 
@@ -127,7 +115,7 @@ a web browser or in Node.js. To enable that, do the following in your `Cargo.tom
 
 ```
 [dependencies]
-rand = { version = "0.7.3", features = ["wasm-bindgen"] }
+rand = { version = "0.8.5", features = ["wasm-bindgen"] }
 ```
 
 Then you must use one of the [`wasm-bindgen`](https://rustwasm.github.io/docs/wasm-bindgen/) compatible tools to instrument