Add formatter option, switch default formatter

We are now using eslint-friendly-formatter as the default, which gives
a small visual representation of where in your code the actual linting
error is. You can override it by following the directions in README.

README.md

@@ -33,5 +33,29 @@ browserify your_file.js -t [ eslintify --extension html --extension haml ]
 
 via JS
 ```js
-.transform({ extensions: ['html', 'haml'] }, eslintify)
+.transform({extensions: ['html', 'haml']}, eslintify)
+```
+
+### other result formatters
+
+Starting with eslintify 2.0, the default formatter is [royriojas/eslint-friendly-formatter](https://github.com/royriojas/eslint-friendly-formatter). You can opt to switch it out for your own choice by providing one of the [eslint official formatter names](http://eslint.org/docs/developer-guide/nodejs-api#getformatter) or a path to a requireable node module.
+
+via CLI
+```bash
+browserify your_file.js -t [ eslintify --formatter json ]
+```
+
+via JS
+```js
+.transform({formatter: 'json'}, eslintify)
+```
+
+custom formatter via CLI
+```bash
+browserify your_file.js -t [ eslintify --formatter ./node_modules/eslint-path-formatter ]
+```
+
+custom formatter via JS
+```bash
+.transform({formatter: './node_modules/eslint-path-formatter'}, eslintify)
 ```

index.js

@@ -3,8 +3,10 @@ var through = require('through');
 var error = console.error.bind(console);
 
 function lint(file, options) {
-    var cli = new eslint.CLIEngine(options || {});
-    var formatter = cli.getFormatter();
+    options = options || {};
+
+    var cli = new eslint.CLIEngine(options);
+    var formatter = cli.getFormatter(options.formatter || __dirname + '/node_modules/eslint-friendly-formatter');
     var data = '';
 
     function write(buf) {

package.json

@@ -7,6 +7,7 @@
   "bugs": "https://github.com/yaycmyk/eslintify/issues",
   "dependencies": {
     "eslint": "^1.0.0",
+    "eslint-friendly-formatter": "^1.2.2",
     "through": "^2.0.0"
   },
   "keywords": [