Fix bug in readme code sample

[IAMOTZ]

Hi there!
I was trying out this mongoose plugin some days ago and I figured one of the code samples in the README is not working as expected. This PR attempts to fixe the issue.

The Issue:
There is this code sample in the README:

Click.create({ip: '127.0.0.1'}, {browser: 'Mozilla'}, function(err, val) {
  Click.findOrCreate({ip: '127.0.0.1'}, {browser: 'Chrome'}, function(err, click) {
    console.log('A click from "%s" using "%s" was found', click.ip, click.browser);
    // prints A click from "127.0.0.1" using "Mozilla" was found
  })
});

When I run this locally, it prints: A click from "127.0.0.1" using "undefined" was found. I figured the first query inserts two different documents({ip: '127.0.0.1'} and {browser: 'Mozilla'}) in the DB, while the second query does nothing since the document matching {ip: '127.0.0.1'} already exists.

The fix:
I updated the code sample to use Click.findOrCreate for the first query:

Click.findOrCreate({ip: '127.0.0.1'}, {browser: 'Mozilla'}, function(err, val) {
  Click.findOrCreate({ip: '127.0.0.1'}, {browser: 'Chrome'}, function(err, click) {
    console.log('A click from "%s" using "%s" was found', click.ip, click.browser);
    // prints A click from "127.0.0.1" using "Mozilla" was found
  })
});

When I run this, it prints the expected message: A click from "127.0.0.1" using "Mozilla" was found. The first query inserts just a single document (merging the first and second argument), while the second query still does nothing since the document matching {ip: '127.0.0.1'} already exists.

[IAMOTZ]

Not sure why the build is failing, I only touched the README file.