chore(package): update nyc to version 15.0.1

Closes #83

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
     "ember-cli": "^3.0.0",
     "lerna": "^2.5.1",
     "loader.js": "^4.6.0",
-    "nyc": "^13.3.0",
+    "nyc": "^15.0.1",
     "qunit": "^2.4.1",
     "rollup-plugin-buble": "^0.19.2",
     "rollup-plugin-sourcemaps": "^0.4.2",