Add Travis-CI setup (#20)

* feat: Run Travis-CI to test rule changes

* chore: npm upgrade for first-heading-level warning

* chore: Add Travis-CI badge

Minor readme formatting

.gitignore

@@ -35,3 +35,6 @@ jspm_packages
 
 # Optional REPL history
 .node_repl_history
+
+# Cloned nodejs/node for testing
+tmp/

.travis.yml

@@ -0,0 +1,7 @@
+language: node_js
+
+node_js: node
+
+before_script: git clone https://github.com/nodejs/node.git tmp
+
+script: npm run travis

README.md

@@ -1,12 +1,17 @@
 # remark-preset-lint-node
+
+[![Build Status](https://travis-ci.com/nodejs/remark-preset-lint-node.svg?branch=master)](https://travis-ci.com/nodejs/remark-preset-lint-node)
+
 remark preset to configure remark-lint with settings for nodejs/node
 
 ## Install
+
 ```console
-$ npm install remark-preset-lint-node
+npm install remark-preset-lint-node
 ```
 
 ## Test
+
 ```console
-$ npm test
+npm test
 ```