added build status to readme

src/0_1_background_information.md

@@ -82,7 +82,7 @@ dynamic dispatch.
 Let's explain this in code instead of words by implementing our own trait
 object from these parts:
 
-```rust, editable
+```rust
 // A reference to a trait object is a fat pointer: (data_ptr, vtable_ptr)
 trait Test {
     fn add(&self) -> i32;

src/0_2_naive_implementation.md

@@ -133,7 +133,7 @@ impl Drop for Reactor {
 }
 ```
 
-```rust, editable
+```rust,editable
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::mpsc::{channel, Sender};
 use std::sync::{Arc, Mutex};