Added a proper GNU GPL LICENSE

Discussed in issue #13, added a license file to be compliant with the GNU GPL license stipulations.

LICENSE

+Wrapper for a PHP MySQL class, which utilizes MySQLi and prepared statements.
+Copyright (C) 2013  Josh Campbell (ajillion)
+
+This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+
+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, see <http://www.gnu.org/licenses/>.