Toggle for wrapping longer lines in 'code' blocks.

@alkemist This is clean version of #342.

## Summary

  - If lines inside 'span.code pre' selector are longer then a screen width, it is very hard to read and interpret results properly.
    - At the bottom of the page check-box will appear, which enables/disables line wrapping.
    - Visually check-box is not distinctive from the footer, but is a part of it.
    - After toggling, it will wrap lines with small amount of CSS.
      - All CSS properties are supported by major browsers (included IE 8 and above).
        - Sources:
          - https://developer.mozilla.org/en-US/docs/Web/CSS/white-space
          - https://developer.mozilla.org/en-US/docs/Web/CSS/word-wrap
          - https://developer.mozilla.org/en-US/docs/Web/CSS/word-break
    - Feature was extensively tested on: 
      - `Firefox`
      - `IE` - from 8 to 11
      - `Google Chrome` and `Chromium`
      - `Opera`
      - All tests were performed on Linux and Windows.
    - As agreed in #342 feature does not use any form of persistence.