build: use nyc for code coverage

.gitignore

@@ -1,3 +1,4 @@
+.nyc_output/
 coverage/
 node_modules/
 npm-debug.log

.travis.yml

@@ -70,10 +70,6 @@ before_install:
     # Configure eslint for linting
     if node_version_lt '8.0'; then npm_remove_module_re '^eslint(-|$)'
     fi
-  - |
-    # Configure istanbul for coverage
-    if node_version_lt '0.10'; then npm_remove_module_re '^istanbul$'
-    fi
   - |
     # Configure mocha for testing
     if   node_version_lt '0.8' ; then npm_use_module 'mocha' '1.21.5'
@@ -82,6 +78,13 @@ before_install:
     elif node_version_lt '6.0' ; then npm_use_module 'mocha' '5.2.0'
     elif node_version_lt '8.0' ; then npm_use_module 'mocha' '6.2.2'
     fi
+  - |
+    # Configure nyc for testing
+    if   node_version_lt '0.10'; then npm_remove_module_re '^nyc$'
+    elif node_version_lt '4.0' ; then npm_use_module 'nyc' '10.3.2'
+    elif node_version_lt '6.0' ; then npm_use_module 'nyc' '11.9.0'
+    elif node_version_lt '8.0' ; then npm_use_module 'nyc' '14.1.1'
+    fi
   # Update Node.js modules
   - |
     # Prune & rebuild node_modules
@@ -105,8 +108,8 @@ script:
     fi
 after_script:
   - |
-    # Upload coverage to coveralls if exists
-    if [[ -e ./coverage/lcov.info ]]; then
+    # Upload coverage to coveralls
+    if [[ -d .nyc_output ]]; then
       npm install --save-dev coveralls@2
-      coveralls < ./coverage/lcov.info
+      nyc report --reporter=text-lcov | coveralls
     fi

package.json

@@ -17,8 +17,8 @@
     "benchmark": "2.1.4",
     "eslint": "6.8.0",
     "eslint-plugin-markdown": "1.0.2",
-    "istanbul": "0.4.5",
-    "mocha": "7.1.1"
+    "mocha": "7.1.1",
+    "nyc": "15.0.1"
   },
   "files": [
     "HISTORY.md",
@@ -33,8 +33,8 @@
     "bench": "node benchmark/index.js",
     "lint": "eslint --plugin markdown --ext js,md .",
     "test": "mocha --reporter spec --bail --check-leaks --ui qunit test/",
-    "test-ci": "istanbul cover node_modules/mocha/bin/_mocha --report lcovonly -- --reporter spec --check-leaks --ui qunit test/",
-    "test-cov": "istanbul cover node_modules/mocha/bin/_mocha -- --reporter dot --check-leaks --ui qunit test/",
+    "test-ci": "nyc --reporter=text npm test",
+    "test-cov": "nyc --reporter=html --reporter=text npm test",
     "version": "node scripts/version-history.js && git add HISTORY.md"
   }
 }