Update NEWS and release PyGObject-2.21.1
Update NEWS and release PyGObject-2.21.1

thiblahute/pygobject,Distrotech/pygobject,pexip/pygobject,alexef/pygobject,jdahlin/pygobject,alexef/pygobject,sfeltman/pygobject,Distrotech/pygobject,davidmalcolm/pygobject,GNOME/pygobject,pexip/pygobject,thiblahute/pygobject,MathieuDuponchelle/pygobject,pexip/pygobject,nzjrs/pygobject,choeger/pygobject-cmake,jdahlin/pygobject,davibe/pygobject,sfeltman/pygobject,alexef/pygobject,davidmalcolm/pygobject,davibe/pygobject,Distrotech/pygobject,nzjrs/pygobject,thiblahute/pygobject,davibe/pygobject,nzjrs/pygobject,GNOME/pygobject,choeger/pygobject-cmake,davidmalcolm/pygobject,choeger/pygobject-cmake,jdahlin/pygobject,sfeltman/pygobject,davibe/pygobject,MathieuDuponchelle/pygobject,Distrotech/pygobject,GNOME/pygobject,MathieuDuponchelle/pygobject