Update dependencies to get ready for node v6

package.json

@@ -13,34 +13,34 @@
   },
   "license": "BSD-2-Clause",
   "engines": {
-    "node": ">=4.2.1 <5"
+    "node": ">=6 <7"
   },
   "scripts": {
     "test": "mocha test/**.js"
   },
   "dependencies": {
-    "@mapbox/mapbox-gl-native": "3.4.4",
+    "@mapbox/mapbox-gl-native": "3.5.4",
+    "@mapbox/mbtiles": "0.9.0",
     "@mapbox/sphericalmercator": "1.0.5",
+    "@mapbox/vector-tile": "1.3.0",
     "advanced-pool": "0.3.2",
     "base64url": "2.0.0",
     "canvas": "1.6.5",
     "clone": "2.1.1",
     "color": "1.0.3",
     "cors": "2.8.3",
-    "express": "4.15.2",
+    "express": "4.15.3",
     "glyph-pbf-composite": "0.0.2",
-    "handlebars": "4.0.8",
+    "handlebars": "4.0.10",
     "http-shutdown": "^1.2.0",
-    "mbtiles": "0.9.0",
-    "morgan": "1.8.1",
+    "morgan": "1.8.2",
     "node-pngquant-native": "1.0.4",
     "nomnom": "1.8.1",
     "pbf": "3.0.5",
     "proj4": "2.4.3",
     "request": "2.81.0",
-    "sharp": "0.17.3",
-    "tileserver-gl-styles": "1.1.1",
-    "vector-tile": "1.3.0"
+    "sharp": "0.18.1",
+    "tileserver-gl-styles": "1.1.1"
   },
   "devDependencies": {
     "should": "^11.2.0",