add note regarding picking one's own students

[Robert]

These threads culminate in a note that one should not select their own student to be a mentee for the program.

https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/google-summer-of-code-mentors-list/X1a2H1TvF5o/sF425LiWAAAJ
https://groups.google.com/d/msgid/google-summer-of-code-mentors-list/CAKPprLLSeEWe2kzAcMBh3Or1Y6sCNWNbV5HOaHwLb3y4p0BUCw%40mail.gmail.com

Also worth mentioning the guidance regarding choosing students from your own school/department.

[Gyan Prakash]

Both the links are showing errors..

[stephanietaylor]

They work if you are on the gsoc-mentors list.