Add coverage using nyc, badge to readme, and ignore the coverage outputs. (#50)

* First pass at mafintosh/dns-packet#48. No auto-refresh yet, because that's a more invasive change.

* Add a quick note to README to kick off a round of tests.

* remove sudo:false

.gitignore

@@ -1 +1,4 @@
-node_modules
+node_modules/
+.nyc_output/
+coverage/
+package-lock.json

.travis.yml

@@ -2,3 +2,10 @@ language: node_js
 node_js:
   - node
   - lts/*
+install:
+- npm install
+- npm install coveralls
+script:
+- npm run coverage
+after_success:
+- npx nyc report --reporter=text-lcov | npx coveralls

README.md

@@ -1,5 +1,5 @@
 # dns-packet
-[![](https://img.shields.io/npm/v/dns-packet.svg?style=flat)](https://www.npmjs.org/package/dns-packet) [![](https://img.shields.io/npm/dm/dns-packet.svg)](https://www.npmjs.org/package/dns-packet) [![](https://api.travis-ci.org/mafintosh/dns-packet.svg?style=flat)](https://travis-ci.org/mafintosh/dns-packet)
+[![](https://img.shields.io/npm/v/dns-packet.svg?style=flat)](https://www.npmjs.org/package/dns-packet) [![](https://img.shields.io/npm/dm/dns-packet.svg)](https://www.npmjs.org/package/dns-packet) [![](https://api.travis-ci.org/mafintosh/dns-packet.svg?style=flat)](https://travis-ci.org/mafintosh/dns-packet) [![Coverage Status](https://coveralls.io/repos/github/mafintosh/dns-packet/badge.svg?branch=master)](https://coveralls.io/github/mafintosh/dns-packet?branch=master)
 
 An [abstract-encoding](https://github.com/mafintosh/abstract-encoding) compliant module for encoding / decoding DNS packets. Lifted out of [multicast-dns](https://github.com/mafintosh/multicast-dns) as a separate module.
 
@@ -251,6 +251,8 @@ And an answer, additional, or authority looks like this
 
 #### `OPT`
 
+[EDNS0](https://tools.ietf.org/html/rfc6891) options.
+
 ``` js
 {
   type: 'OPT',

package.json

@@ -10,7 +10,11 @@
     "node": ">=6"
   },
   "scripts": {
-    "test": "eslint --color *.js examples/*.js && tape test.js"
+    "clean": "rm -rf coverage .nyc_output/",
+    "lint": "eslint --color *.js examples/*.js",
+    "pretest": "npm run lint",
+    "test": "tape test.js",
+    "coverage": "nyc -r html npm test"
   },
   "dependencies": {
     "ip": "^1.1.5"
@@ -22,6 +26,7 @@
     "eslint-plugin-node": "^8.0.1",
     "eslint-plugin-promise": "^4.0.1",
     "eslint-plugin-standard": "^4.0.0",
+    "nyc": "^13.3.0",
     "tape": "^4.10.1"
   },
   "keywords": [