Undo recent buggy change that made NewSpanVariable an AutoDiff, and added a comment to make sure I don't do it again.
Undo recent buggy change that made NewSpanVariable an AutoDiff, and added a comment to make sure I don't do it again.

pogren-oracle/factorie,digitalreasoning/factorie-scala-210,patverga/factorie,melisabok/factorie,asubbaswamy/factorie,joprice/factorie,strubell/factorie,Craigacp/factorie,hlin117/factorie,zxsted/factorie,malcolmgreaves/factorie,factorie/factorie