Tweak travis-ci.org matrix a bit
Tweak travis-ci.org matrix a bit

 * REE is just 1.8.7. For projects that go over 20 rows in the build matrix, we suggest that REE is not included
 * rbx-2.0 will soon become rbx (master) so rbx is basically obsolete now
 * we provide 1.9.3[-preview1]
JuanitoFatas/slim,yterajima/slim,ruijsun/slim,raxoft/slim,sideci-sample/sideci-sample-slim,zakuro9715/slim,JuanitoFatas/slim,zakuro9715/slim,metallurgical/slim,Nikeshsuwal/slim,cheunghy/slim,slim-template/slim,fly19890211/slim,XueQian/slim,cheunghy/slim,slim-template/slim,etdev/slim,ericboehs/slim,ericboehs/slim,XueQian/slim,etdev/slim,metallurgical/slim,mojavelinux/slim,fly19890211/slim,ruijsun/slim,mojavelinux/slim,Nikeshsuwal/slim,raxoft/slim,slim-template/slim