ci(travis): move coveralls script from package.json to .travis.yml

Use `npx` so we can remove `coveralls` from devDependencies

Author: remarkablemark

.travis.yml

@@ -12,7 +12,7 @@ script:
   - npm run build
   - npm run benchmark
 after_success:
-  - npm run coveralls
+  - npx nyc report --reporter=text-lcov | npx coveralls
 cache:
   directories:
     - node_modules

package.json

@@ -10,7 +10,6 @@
     "build:min": "cross-env NODE_ENV=production rollup --config --file dist/html-react-parser.min.js --sourcemap",
     "build:unmin": "cross-env NODE_ENV=development rollup --config --file dist/html-react-parser.js",
     "clean": "rimraf dist",
-    "coveralls": "nyc report --reporter=text-lcov | coveralls",
     "lint": "eslint --ignore-path .gitignore --ignore-pattern /examples/ .",
     "lint:dts": "dtslint .",
     "lint:fix": "npm run lint -- --fix",
@@ -45,7 +44,6 @@
     "@commitlint/config-conventional": "^8.2.0",
     "@types/react": "^16.9.11",
     "benchmark": "^2.1.4",
-    "coveralls": "^3.0.7",
     "cross-env": "^6.0.3",
     "dtslint": "^2.0.0",
     "eslint": "^6.6.0",