Add interface for require function

[hubjac1]

I have add the possibility to call csv-test from node using classic require function.

An example usage might look like this:

var config = fs.readFileSync('path/to/config.yml', 'utf8'),
    stream = fs.createReadStream(path/to/data.csv, 'utf8');

require('csv-test')(config, stream, undefined, function(errors) {
    // handle list of errors.
    console.error(errors)
});