updated tutorial index page - minor edits
updated tutorial index page - minor edits

usc-isi-i2/usc-isi-i2.github.io,usc-isi-i2/usc-isi-i2.github.io,usc-isi-i2/usc-isi-i2.github.io,usc-isi-i2/usc-isi-i2.github.io