[Tests] switch from nsp to npm audit

.npmrc

@@ -1 +1,2 @@
 package-lock=false
+audit-level=high

.travis.yml

@@ -260,3 +260,4 @@ matrix:
     - os: osx
     - env: TEST=true ALLOW_FAILURE=true
     - env: COVERAGE=true
+    - env: POSTTEST=true

package.json

@@ -9,12 +9,14 @@
 		"pretest": "npm run lint",
 		"test": "npm run tests-only",
 		"tests-only": "node --harmony --es-staging test.js",
-		"posttest": "npm run security",
+		"posttest": "npm run audit",
 		"coverage": "covert test.js",
 		"coverage-quiet": "covert test.js --quiet",
 		"lint": "eslint test.js *.js",
 		"eccheck": "editorconfig-tools check *.js **/*.js > /dev/null",
-		"security": "nsp check"
+		"preaudit": "npm install --package-lock --package-lock-only",
+		"audit": "npm audit",
+		"postaudit": "rm package-lock.json"
 	},
 	"repository": {
 		"type": "git",