Metrics module for Graylog

The Metrics module for logging (node.js > 4.*).
Uses graylog2

#### For example log response time from Google
`` js
const Metrics = require('xpm-metrics-graylog');
const metrics = new Metrics({
servers: [
{
host: 'www.xpm.tech',
port: 12201
}
],
hostname: 'example.host'
});
const request = require('request-promise');
const params = {
uri: 'https://www.google.com',
resolveWithFullResponse: true,
time: true
};

request(params)
.then((res) => metrics.logTime('google_response', res.elapsedTime, 'test'));
``