Update dependencies.

Author: jonkemp

package.json

@@ -15,15 +15,15 @@
     "flatten": "^1.0.2",
     "object.pick": "^1.3.0",
     "slick": "^1.12.2",
-    "specificity": "^0.3.2"
+    "specificity": "^0.4.1"
   },
   "devDependencies": {
     "coveralls": "^3.0.0",
     "gulp": "^3.9.1",
-    "gulp-eslint": "^4.0.2",
-    "gulp-mocha": "^5.0.0",
+    "gulp-eslint": "^5.0.0",
+    "gulp-mocha": "^6.0.0",
     "mocha": "^5.0.4",
-    "nyc": "^11.4.1",
+    "nyc": "^13.1.0",
     "should": "*",
     "vinyl": "^2.1.0"
   },