Formatting issues in exported-files.md

[bigteejay]

https://github.com/oat-sa/taohub-articles/blob/master/forge/Developer%20Guide/exported-files.md

The content following the field headers ("item identifier value test_taker") ends up being incorrectly rendered as clickable links in both Chrome and Firefox... making following/reading this document very difficult at best (you can, however, view the raw source of the file and have a little better luck.)

Somewhat similar to issue #22 (a scrollable region will probably be very helpful once the content rendering is addressed.)