Replace istanbul with nyc

Author: wooorm

.gitignore

@@ -1,5 +1,6 @@
 .DS_Store
 *.log
+.nyc_output/
 coverage/
 node_modules/
 nlcst-to-string.js

package.json

@@ -26,7 +26,7 @@
   "devDependencies": {
     "browserify": "^13.0.1",
     "esmangle": "^1.0.1",
-    "istanbul": "^0.4.0",
+    "nyc": "^9.0.1",
     "remark-cli": "^2.0.0",
     "remark-preset-wooorm": "^1.0.0",
     "tape": "^4.0.0",
@@ -40,9 +40,15 @@
     "build": "npm run build-md && npm run build-bundle && npm run build-mangle",
     "lint": "xo",
     "test-api": "node test.js",
-    "test-coverage": "istanbul cover test.js",
+    "test-coverage": "nyc --reporter lcov tape test.js",
     "test": "npm run build && npm run lint && npm run test-coverage"
   },
+  "nyc": {
+    "check-coverage": true,
+    "lines": 100,
+    "functions": 100,
+    "branches": 100
+  },
   "xo": {
     "space": true,
     "ignore": [