Add code coverage using NYC and integrate with codecov

.gitignore

@@ -2,3 +2,5 @@
 *.log
 node_modules
 lib
+.nyc_output
+coverage

.travis.yml

@@ -3,4 +3,20 @@ node_js:
   - 4
   - 5
   - 6
-script: "npm run travis"
+
+cache:
+  directories:
+  - node_modules
+
+before_script:
+- npm run lint
+- npm run prepublish
+
+script:
+- npm run test
+- npm run system-test
+- npm run check-coverage
+- npm run report-coverage
+
+after_script:
+- npm run codecov

package.json

@@ -5,8 +5,13 @@
   "main": "index.js",
   "scripts": {
     "prepublish": "rm -rf lib/ && babel src/ --out-dir lib/",
+    "system-test": "mocha --compilers js:babel-register \"system-test/**/*Test.js\"",
+    "check-coverage": "npm run cover && nyc check-coverage --statements 80 --branches 80 --functions 80",
+    "report-coverage": "nyc report --reporter=lcov",
+    "cover": "nyc npm t",
+    "codecov": "cat coverage/*/lcov.info | codecov",
     "lint": "eslint src/ test/ bin/ *.js",
-    "test": "npm run prepublish && mocha --compilers js:babel-register \"test/**/*Test.js\"",
+    "test": "mocha --compilers js:babel-register \"test/**/*Test.js\"",
     "watch": "mocha --watch --compilers js:babel-register \"test/transform/**/*Test.js\"",
     "travis": "npm run lint && npm run test"
   },
@@ -56,8 +61,10 @@
     "babel-preset-es2015": "^6.9.0",
     "babel-register": "^6.11.6",
     "chai": "^3.4.1",
+    "codecov": "^1.0.1",
     "eslint": "^3.3.0",
     "eslint-plugin-no-null": "^1.0.1",
-    "mocha": "^2.3.4"
+    "mocha": "^2.3.4",
+    "nyc": "^10.1.2"
   }
 }