Add clean task; fix up dependencies

package.json

@@ -32,16 +32,15 @@
     "babel-plugin-transform-runtime": "^6.23.0",
     "babel-preset-env": "^1.5.1",
     "babel-register": "^6.24.1",
-    "chai": "^3.5.0",
-    "chai-as-promised": "^6.0.0",
+    "chai": "^4.0.2",
+    "chai-as-promised": "^7.0.0",
     "coveralls": "^2.13.1",
-    "del": "^2.2.0",
     "delay": "^2.0.0",
     "in-publish": "^2.0.0",
+    "mocha": "^3.4.2",
     "mocha-junit-reporter": "^1.13.0",
-    "nyc": "^10.3.2",
+    "nyc": "^11.0.3",
     "rimraf": "^2.6.1",
-    "run-sequence": "^1.2.1",
     "sinon": "^2.3.1",
     "sinon-chai": "^2.10.0",
     "standard": "^10.0.2"
@@ -53,7 +52,8 @@
   ],
   "scripts": {
     "prepublish": "in-publish && npm run build || not-in-publish",
-    "build": "rimraf lib && babel src --out-dir lib",
+    "clean": "rimraf lib",
+    "build": "npm run clean && babel src --out-dir lib",
     "test": "npm run test:lint && npm run test:cover",
     "test:lint": "standard",
     "test:unit": "mocha --compilers js:babel-register test/lib/setup.js test/**/*.spec.js",