Add node v6
Add node v6

mapbox/node-pre-gyp,mojodna/node-pre-gyp,mojodna/node-pre-gyp,mojodna/node-pre-gyp,mojodna/node-pre-gyp,mapbox/node-pre-gyp,mojodna/node-pre-gyp,mapbox/node-pre-gyp,mapbox/node-pre-gyp,mapbox/node-pre-gyp