Add recent contributors to credits

I trust none of the contributors object to being mentioned. So I took stats of the last few hundred commits and the top contributors:
git log --format='%an - %ae' | head -n 500 | sort | uniq -c | sort -nk 1

No doubt it isn't complete, but if anyone was forgotten, then no doubt he/she will be added next time around. :)

I also will credit those contributors in APG, unless someone doesn't want to be mentioned for some reason.
I'll send an email to everybody regarding that.