update node version for travis ci
update node version for travis ci

geoffp/patternlab-node,pattern-lab/patternlab-node,pattern-lab/patternlab-node,heedfull/ClionaJoycePatterns,geoffp/patternlab-node,heedfull/ClionaJoycePatterns,pattern-lab/patternlab-node,stevemartin/patternlab-node,pattern-lab/patternlab-node,pattern-lab/patternengine-node-mustache,stevemartin/patternlab-node