Long lines in code blocks should be split

- If lines inside 'span.code pre' selector are longer than a screen width, it is very hard to read and interpret results properly.
- It is only a small but IMHO needed CSS fix.
- There is no change regarding logic or behaviour.
  - All CSS properties are supported by major browsers (including IE 8 and above).
  - Sources:
    - https://developer.mozilla.org/en-US/docs/Web/CSS/word-wrap
    - https://developer.mozilla.org/en-US/docs/Web/CSS/white-space
    - https://developer.mozilla.org/en-US/docs/Web/CSS/word-break