added nyc coverage

Author: toybz

src/.nycrc

@@ -0,0 +1,10 @@
+ {
+   "coverage": "test",
+   "check-coverage": true,
+   "functions": 50,
+   "lines": 50,
+   "report-dir": "./coverage",
+   "reporter": [
+     "lcov"
+   ]
+ }