Mark non-runnable examples

Author: dhardy

src/guide-dist.md

@@ -93,7 +93,7 @@ Lets go over the distributions by type:
     support requires using the `simd_support` feature flag and nightly `rustc`.
 -   For enums, you have to implement uniform sampling yourself. For example, you
     could use the following approach:
-    ```rust
+    ```rust,noplayground
     # use rand::{Rng, distr::{Distribution, StandardUniform}};
     pub enum Food {
         Burger,

src/guide-test-fn-rng.md

@@ -43,7 +43,7 @@ fn main() {
 
 To test this, we can create a `MockCryptoRng` implementing `TryRngCore` and `TryCryptoRng` in our testing module. Note that `MockCryptoRng` is private and `#[cfg(test)] mod tests` is cfg-gated to our test environment, thus ensuring that `MockCryptoRng` cannot accidentally be used in production.
 
-```rust
+```rust,noplayground
 #[cfg(test)]
 mod tests {
     use super::*;

src/update-0.5.md

@@ -74,7 +74,7 @@ A new trait has been added: `FromEntropy`. This is automatically implemented for
 any type supporting `SeedableRng`, and provides construction from fresh, strong
 entropy:
 
-```rust
+```rust,noplayground
 use rand_0_5::{ChaChaRng, FromEntropy};
 
 let mut rng = ChaChaRng::from_entropy();
@@ -120,7 +120,8 @@ use cannot be guaranteed.*
 A new `Error` type has been added, designed explicitly for no-std compatibility,
 simplicity, and enough flexibility for our uses (carrying a `cause` when
 possible):
-```ignore
+```rust,noplayground
+# use rand_0_5::ErrorKind;
 pub struct Error {
     pub kind: ErrorKind,
     pub msg: &'static str,
@@ -181,7 +182,7 @@ The method `ChaChaRng::set_counter` has been replaced by two new methods,
 `set_word_pos` and `set_stream`. Where necessary, the behaviour of the old
 method may be emulated as follows:
 
-```rust
+```rust,noplayground
 # extern crate rand;
 # extern crate rand_chacha;
 # use rand::prelude::*;

src/update-0.7.md

@@ -23,7 +23,7 @@ The [`FromEntropy`] trait has now been removed. Fear not though, its
 [`from_entropy`] method continues to provide easy initialisation from its new
 home in the [`SeedableRng`] trait (this requires that `rand_core` has the `std`
 or `getrandom` feature enabled):
-```rust
+```rust,noplayground
 # extern crate rand_0_7 as rand;
 use rand::{SeedableRng, rngs::StdRng};
 let mut rng = StdRng::from_entropy();

src/update-0.8.md

@@ -52,7 +52,7 @@ let a: u32 = Standard.sample_iter(rng).next().unwrap();
 let b: u32 = Standard.sample_iter(rng).next().unwrap();
 ```
 can be replaced with the following code:
-```rust
+```rust,noplayground
 # extern crate rand;
 # use rand_0_8::prelude::*;
 # use rand_0_8::distributions::Standard;
@@ -130,7 +130,7 @@ Several smaller changes occurred to rand distributions:
         .collect();
     ```
     With Rand 0.8, this is equivalent to the following:
-    ```rust
+    ```rust,noplayground
     # extern crate rand;
     # use rand_0_8::{distributions::Alphanumeric, Rng};
     # fn main() {