is-utf8

#utf8 detector

Detect if a Buffer is utf8 encoded.
It need The minimum amount of bytes is 4.

``javascript
var fs = require('fs');
var isUtf8 = require('is-utf8');
var ansi = fs.readFileSync('ansi.txt');
var utf8 = fs.readFileSync('utf8.txt');

console.log('ansi.txt is utf8: '+isUtf8(ansi)); //false
console.log('utf8.txt is utf8: '+isUtf8(utf8)); //true
``