Add languages to relevant fenced code blocks

See http://azerupi.github.io/mdBook/format/theme/syntax-highlighting.html

src/design/url/urls.md

@@ -27,7 +27,7 @@ URLs can be opened, yielding _schemes_, which can be opened to resources, which
 
 For compatibility reasons, we use a file API similar to the Rust standard libraries for opening URLs:
 
-```
+```rust
 use std::fs::OpenOptions;
 use std::io::prelude::*;
 

src/getting_started/compiling_redox.md

@@ -6,7 +6,7 @@ Now we have prepared the build, so naturally we're going to build Redox.
 Cloning the repository
 ----------------------
 
-```
+```sh
 $ git clone https://github.com/redox-os/redox.git; git submodule update --init
 ```
 
@@ -15,7 +15,7 @@ Give it a while. Redox is big.
 Yay! Building!
 --------------
 
-```
+```sh
 $ cd /path/to/redox
 $ make -j 4 build
 ```
@@ -28,7 +28,7 @@ Running Redox
 -------------
 
 To run Redox, do:
-```
+```sh
 $ make qemu
 ```
 
@@ -36,7 +36,7 @@ This should open up a Qemu window, booting to Redox.
 
 If it does not work, try:
 
-```
+```sh
 $ make qemu kvm=no # we disable KVM
 ```
 

src/getting_started/exploring_redox.md

@@ -29,7 +29,7 @@ Rusthello is an advanced Reversi AI, made by [Enrico](https://github.com/EGhiorz
 
 Oh, let's try it out!
 
-```
+```sh
 # first we `cd` to the Rusthello directory
 $ cd apps/rusthello
 # now, run the binary file

src/getting_started/preparing_the_build.md

@@ -5,7 +5,7 @@ Woah! You made it so far, all the way to here. Congrats! Now we gotta build Redo
 
 _If you're lazy, and on an Linux computer. Well, you're today's winner! Just run the bootstrapping script, which does the build preparation for you:_
 
-```
+```sh
 $ curl -sf https://raw.githubusercontent.com/redox-os/redox/master/bootstrap.sh -o bootstrap.sh && bash -e bootstrap.sh
 ```
 
@@ -25,12 +25,12 @@ While the following step is not _required_, it is recommended. If you already ha
 
 We will use `multirust` to manage our Rust versions:
 
-```
+```sh
 $ curl -sf https://raw.githubusercontent.com/brson/multirust/master/quick-install.sh | sh
 ```
 
 Now, we have to configure our multirust installation to default to `nightly`:
 
-```
+```sh
 $ multirust override nightly
 ```