Update "Built using..." Copyright to be current year

[rachelbaker]

The year for the license Copyright is dynamic in the plugin.php file, but the 10up, LLC Copyright year is hardcoded in the plugin.php file.

Resulting in this in the head of a generated plugin.php file:

/**
 * Copyright (c) 2014 Rachel Baker (email : rachel@rachelbaker.me)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2 or, at
 * your discretion, any later version, as published by the Free
 * Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

/**
 * Built using grunt-wp-plugin
 * Copyright (c) 2013 10up, LLC
 * https://github.com/10up/grunt-wp-plugin
 */

It would look much cleaner if we used {%= grunt.template.today('yyyy') %} for the year in the 10up, LLC Copyright block so the two years match.