Added a NNID warnings and removed outdated info on Juxt

[piplupness]

Resolves #374

Changes:

Added a disclaimer about not removing your NNID and fixed outdated info (Juxtaposition is public for almost a year now and rverse is currently dead)

• [x] I have read and agreed to the Code of Conduct.
• [x] I have read and complied with the contributing guidelines.
• [ ] What I'm implementing was an approved issue.
• [x] I have tested all of my changes.

[MiniBioOne]

i think it'd be better to say "your NNID" instead of "the NNID"