[fix bug 881792] Add icon for Mozillians link

Add new Mozillians icon in image sprite for Mozillians field in user
profiles.

Signed-off-by: Kaustav Das Modak <kaustav.dasmodak@yahoo.co.in>
Merge pull request #1470 from kaustavdm/mozillians-field-881792

[fix bug 881792] Add icon for Mozillians link