Add nyc for code coverage

.gitignore

@@ -15,3 +15,4 @@ npm-debug.log
 /node_modules
 coverage
 .idea
+.nyc_output

.travis.yml

@@ -4,3 +4,7 @@ node_js:
   - "7"
   - "6"
   - "4"
+
+after_success:
+  - npm install coveralls
+  - npm run coverage && cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js && rm -rf ./coverage

package.json

@@ -12,7 +12,8 @@
     "test-source-map": "webpack-dev-server --config test/sourceMap/webpack.config.js --content-base ./test/sourceMap --inline",
     "test-watch": "webpack --config test/watch/webpack.config.js",
     "test-extract-text": "webpack --config test/extractText/webpack.config.js",
-    "test-hmr": "webpack-dev-server --config test/hmr/webpack.config.js --content-base ./test/hmr --hot --inline"
+    "test-hmr": "webpack-dev-server --config test/hmr/webpack.config.js --content-base ./test/hmr --hot --inline",
+    "coverage": "nyc --reporter=lcov npm test"
   },
   "keywords": [
     "sass",
@@ -46,6 +47,7 @@
     "file-loader": "^0.10.0",
     "mocha": "^3.0.2",
     "node-sass": "^4.5.0",
+    "nyc": "^10.1.2",
     "raw-loader": "^0.5.1",
     "should": "^11.2.0",
     "style-loader": "^0.13.1",