Use $ consistently in bash scripts and apply bash syntax highlighting (…

…closes #760,#691).

content/tokio/tutorial/channels.md

@@ -6,28 +6,28 @@ Now that we have learned a bit about concurrency with Tokio, let's apply this on
 the client side. Put the server code we wrote before into an explicit binary
 file:
 
-```text
-mkdir src/bin
-mv src/main.rs src/bin/server.rs
+```bash
+$ mkdir src/bin
+$ mv src/main.rs src/bin/server.rs
 ```
 
 and create a new binary file that will contain the client code:
 
-```text
-touch src/bin/client.rs
+```bash
+$ touch src/bin/client.rs
 ```
 
 In this file you will write this page's code. Whenever you want to run it,
 you will have to launch the server first in a separate terminal window:
 
-```text
-cargo run --bin server
+```bash
+$ cargo run --bin server
 ```
 
 And then the client, __separately__:
 
-```text
-cargo run --bin client
+```bash
+$ cargo run --bin client
 ```
 
 That being said, let's code!

content/tokio/tutorial/io.md

@@ -163,14 +163,14 @@ To start, we will implement the echo logic using the [`io::copy`][copy] utility.
 
 You can write up this code in a new binary file:
 
-```text
-touch src/bin/echo-server-copy.rs
+```bash
+$ touch src/bin/echo-server-copy.rs
 ```
 
 That you can launch (or just check the compilation) with:
 
-```text
-cargo run --bin echo-server-copy
+```bash
+$ cargo run --bin echo-server-copy
 ```
 
 You will be able to try the server using a standard command-line tool such as `telnet`, or by writing

content/tokio/tutorial/streams.md

@@ -152,7 +152,7 @@ If you hit an error message like this, try pinning the value!
 
 Before trying to run this, start the Mini-Redis server:
 
-```text
+```bash
 $ mini-redis-server
 ```