gun_1.blend edited, gun_1.png and gun_1.tga created for issue #66:

 - gun_1.tga is the image used by gun_1.blend.
 - gun_1.blend has the final version of the gun + a right arm made from
   the left arm already done.
Merge branch 'Grupo-A' of https://github.com/eloipuertas/ES2013Dimarts into Grupo-A