Some of the tool rental centers have a scraping machine that is most often used to remove vinyl flooring and adhesive. Seeing that there are no nails holding down the wood, only adhesive, check with them to see if the machine will do that job. Other than that, manual scraping and lifting with a pry bar is the only way I see. You will need to remove the glue as much as possible to create a better bond for the tile thinset. Be careful about using petroleum based solvents, they leave a non-bonding residue behind in the cement. Some modified thinsets are rated to go over cutback adhesive, so that is the kind you want. Dont trust the advice at the big box stores, go to a tile retail store to get the thinset.