travis.yml: bump appengine dependency
travis.yml: bump appengine dependency

This is currently breaking CI. We should ultimately find a better place
to download this binary, because Google doesn't seem to host old
versions for very long.

1d4Nf6/cayley,dtkav/cayley,skynet/cayley,1d4Nf6/cayley,googlearchive/cayley,barakmich/cayley,praisondani/cayley,pombredanne/cayley,agupta666/cayley,jzelinskie/cayley,kortschak/cayley,dtkav/cayley,sayden/cayley,skynet/cayley,drhodes/cayley,praisondani/cayley,gmbuell/cayley,HomeMango0310/cayley,ominux/cayley,deskr/cayley,deskr/cayley,googlearchive/cayley,kortschak/cayley,deskr/cayley,HomeMango0310/cayley,1d4Nf6/cayley,samanalysis/cayley,drhodes/cayley,gmbuell/cayley,h4ck3rm1k3/cayley,barakmich/cayley,Kavec/cayley,agupta666/cayley,gmbuell/cayley,jzelinskie/cayley,cayleygraph/cayley,abhishekgahlot/cayley,abhishekgahlot/cayley,jacobxk/cayley,Kavec/cayley,jacobxk/cayley,h4ck3rm1k3/cayley,sayden/cayley,zorojean/cayley,drhodes/cayley,dushmis/cayley,cayleygraph/cayley,sdaros/cayley,OrenBochman/cayley,sdaros/cayley,h4ck3rm1k3/cayley,mjolk/cayley,barakmich/cayley,azylman/cayley,samanalysis/cayley,pombredanne/cayley,kortschak/cayley,posenhuang/cayley,ominux/cayley,kortschak/cayley,dtkav/cayley,ominux/cayley,h4ck3rm1k3/cayley,sdaros/cayley,HomeMango0310/cayley,sayden/cayley,googlearchive/cayley,h4ck3rm1k3/cayley,deskr/cayley,azylman/cayley,OrenBochman/cayley,deskr/cayley,mjolk/cayley,zorojean/cayley,jacobxk/cayley,googlearchive/cayley,pombredanne/cayley,mjolk/cayley,barakmich/cayley,HomeMango0310/cayley,jzelinskie/cayley,jzelinskie/cayley,sayden/cayley,abhishekgahlot/cayley,samanalysis/cayley,Kavec/cayley,mjolk/cayley,agupta666/cayley,skynet/cayley,beni55/cayley,ominux/cayley,praisondani/cayley,posenhuang/cayley,dushmis/cayley,kortschak/cayley,zorojean/cayley,drhodes/cayley,samanalysis/cayley,praisondani/cayley,pombredanne/cayley,skynet/cayley,zorojean/cayley,dushmis/cayley,OrenBochman/cayley,azylman/cayley,beni55/cayley,dtkav/cayley,1d4Nf6/cayley,dushmis/cayley,Kavec/cayley,posenhuang/cayley,gmbuell/cayley,barakmich/cayley,sdaros/cayley,OrenBochman/cayley,beni55/cayley,jacobxk/cayley,abhishekgahlot/cayley,azylman/cayley,agupta666/cayley,posenhuang/cayley,beni55/cayley