especially the safety instructions about open flame, ventilation and etc., you should be able to clean this up using Jasco adhesive remover. You can get it at HD, Lowes, hardware store etc..
Working small areas at a time you can brush it on like a paint stripper and remove the mastic with Scotchbrite or steel wool. If you have glue in the grout, you may have to regrout. A seemingly knowledgeable poster named Hy recommends products from Peelaway.com. I haven't tried their products yet, but am amenable to finding less toxic products. Luck, Kizmet