generate html and lcov coverage reports

package.json

@@ -11,9 +11,9 @@
     "pretest": "npm run build",
     "test": "mocha",
     "pretest-coverage": "npm run build",
-    "test-coverage": "istanbul cover --report json node_modules/.bin/_mocha -- -u exports -R spec test/test.js",
-    "posttest-coverage": "remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped.json -b dist",
-    "ci": "npm run test-coverage && codecov < coverage/coverage-remapped.json",
+    "test-coverage": "rm -rf coverage/* && istanbul cover --report json node_modules/.bin/_mocha -- -u exports -R spec test/test.js",
+    "posttest-coverage": "remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped.json -b dist && remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped.lcov -t lcovonly -b dist && remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped -t html -b dist",
+    "ci": "npm run test-coverage && codecov < coverage/coverage-remapped.lcov",
     "build": "gobble build -f dist",
     "prepublish": "npm test",
     "lint": "eslint src"