Fix up code markdown. Renders better in browser and editor

Inline code should be backticked _once_ i.e. `function_name`.

Code blocks should use three backticks and a newline and a language where
appropriate... e.g.

```ocaml
let f () = ()
```

Carry on here...

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>