Add licenses to gulp stream.

Install this package with npm and add it to your development dependencies:

npm install --save-dev gulp-license

var gulp = require('gulp');
var license = require('gulp-license');
var pump = require('pump');

gulp.task('license', function (cb) {
  pump([
      gulp.src('./lib/*.js'),
      license('MIT', {tiny: true}),
      gulp.dest('./dist')
    ],
    cb
  );
});

To help properly handle error conditions with Node streams, this project recommends the use of pump. For more information, see Why Use Pump?