Update dev-dependencies

Author: wooorm

Diff for: package.json

@@ -30,13 +30,13 @@
   "dependencies": {},
   "devDependencies": {
     "browserify": "^16.0.0",
-    "nyc": "^14.0.0",
+    "nyc": "^15.0.0",
     "prettier": "^1.0.0",
     "remark-cli": "^7.0.0",
     "remark-preset-wooorm": "^6.0.0",
     "tape": "^4.0.0",
     "tinyify": "^2.0.0",
-    "xo": "^0.25.0"
+    "xo": "^0.27.0"
   },
   "scripts": {
     "format": "remark . -qfo && prettier --write \"**/*.js\" && xo --fix",