Agregada licencia y guia de uso rápido en readme

*    This file is part of the gasotransmitter dosificator project.
*
*    Singularity is free software, hardware and data; 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, or (at
your
*    option) any later version.
*
*    Singularity 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 GCC; see the file COPYING3.  If not see
*    <http://www.gnu.org/licenses/>.