update dependencies

package.json

@@ -33,21 +33,21 @@
     "node": ">=0.5.x"
   },
   "dependencies": {
-    "chroma-js": "~1.2.1",
+    "chroma-js": "~1.3.3",
     "hsluv": "~0.0.1",
-    "js-yaml": "~3.7.0",
+    "js-yaml": "~3.8.4",
     "lodash": "~4.17.2",
     "mapnik-reference": "~8.6.1",
     "semver": "~5.3.0",
-    "yargs": "~6.6.0"
+    "yargs": "~8.0.1"
   },
   "optionalDependencies": {
     "millstone": "~0.6.17"
   },
   "devDependencies": {
-    "coveralls": "~2.11.15",
+    "coveralls": "~2.13.1",
     "istanbul": "~0.4.5",
-    "mocha": "~3.2.0",
+    "mocha": "~3.4.1",
     "mocha-eslint": "^3.0.1",
     "sax": "~1.2.1"
   },