Update node.js versions in travis
Update node.js versions in travis

mysticatea/acorn,ternjs/acorn,mysticatea/acorn,marijnh/acorn,marijnh/acorn,marijnh/acorn,TimothyGu/acorn,ternjs/acorn,TimothyGu/acorn,TimothyGu/acorn,mysticatea/acorn,ternjs/acorn