ci(tests): make coverage generate lcov.info file

Author: jankapunkt

package.json

@@ -38,7 +38,7 @@
     "pretest": "./node_modules/.bin/eslint lib test index.js",
     "test": "NODE_ENV=test ./node_modules/.bin/mocha 'test/**/*_test.js'",
     "test-debug": "NODE_ENV=test ./node_modules/.bin/mocha  --inspect --debug-brk 'test/**/*_test.js'",
-    "test:coverage": "NODE_ENV=test nyc --reporter=html --reporter=text ./node_modules/.bin/mocha 'test/**/*_test.js'"
+    "test:coverage": "NODE_ENV=test nyc --report=lcovonly --reporter=text ./node_modules/.bin/mocha 'test/**/*_test.js'"
   },
   "repository": {
     "type": "git",