update tsconfig.json for 1.5.3 (does not presently have an effect).
update tsconfig.json for 1.5.3 (does not presently have an effect).

TypeStrong/grunt-ts,vp2177/grunt-ts,vp2177/grunt-ts,TypeStrong/grunt-ts,sethx/grunt-ts,sethx/grunt-ts,TypeStrong/grunt-ts,sethx/grunt-ts,vp2177/grunt-ts