Bump to GWT 2.6.0.
Bump to GWT 2.6.0.

rachelharvey/playn,playn/playn,tinkerstudent/playn,rachelharvey/playn,longtaoge/playn,playn/playn,ruslansennov/playn2,ruslansennov/playn2,thecocce/playn-1,tinkerstudent/playn,longtaoge/playn,thecocce/playn-1,playn/playn