Add challenge description

README.md

 Rust implementation of [golang challenge #1](http://golang-challenge.org/go-challenge1).
 
 A simple binary file format for a drum machine is given. The task is to reverse
-it and implement a decoder it.
+it and implement a decoder for it.
+
+## Example output
+
+With the challenge came some examples how the lost executable's outputs looked
+like. In `fixtures/` are all the example binaries given. And in `src/tests.rs`
+are the respective example outputs.
+
+```
+Saved with HW Version: 0.808-alpha
+Tempo: 120
+(0) kick	|x---|x---|x---|x---|
+(1) snare	|----|x---|----|x---|
+(2) clap	|----|x-x-|----|----|
+(3) hh-open	|--x-|--x-|x-x-|--x-|
+(4) hh-close	|x---|x---|----|x--x|
+(5) cowbell	|----|----|--x-|----|
+```
 
 ## File format
 
@@ -27,7 +44,7 @@ Size | Encoding | Description
  1   | u8       | id
  4   | u32      | length of the name field (n_l)
  n   | ASCII    | name
-16   | bool[]   | data (encoded as information when to hit)
+16   | bool[]   | data (byte-wise when to hit: 0 for no, 1 for yes)
 
 ## To-do