[fix] add missing gecko executable to travis
[fix] add missing gecko executable to travis

matejc/searx,misnyo/searx,jcherqui/searx,jibe-b/searx,jibe-b/searx,PwnArt1st/searx,misnyo/searx,asciimoo/searx,asciimoo/searx,jcherqui/searx,asciimoo/searx,potato/searx,misnyo/searx,potato/searx,potato/searx,jibe-b/searx,potato/searx,dalf/searx,jcherqui/searx,asciimoo/searx,dalf/searx,jibe-b/searx,PwnArt1st/searx,dalf/searx,jcherqui/searx,PwnArt1st/searx,PwnArt1st/searx,misnyo/searx,dalf/searx,matejc/searx,matejc/searx,matejc/searx