Add stackbrew and update scripts, more specific ruby

```console
$ ./generate-stackbrew-library.sh
# maintainer: InfoSiftr <github@infosiftr.com> (@infosiftr)

4.1.4: git://github.com/docker-library/rails@d90069dcad89d6fd21c8a6c0490eaf1119774ba9
4.1: git://github.com/docker-library/rails@d90069dcad89d6fd21c8a6c0490eaf1119774ba9
4: git://github.com/docker-library/rails@d90069dcad89d6fd21c8a6c0490eaf1119774ba9
latest: git://github.com/docker-library/rails@d90069dcad89d6fd21c8a6c0490eaf1119774ba9

4.1.4-onbuild: git://github.com/docker-library/rails@d90069dcad89d6fd21c8a6c0490eaf1119774ba9 onbuild
4.1-onbuild: git://github.com/docker-library/rails@d90069dcad89d6fd21c8a6c0490eaf1119774ba9 onbuild
4-onbuild: git://github.com/docker-library/rails@d90069dcad89d6fd21c8a6c0490eaf1119774ba9 onbuild
onbuild: git://github.com/docker-library/rails@d90069dcad89d6fd21c8a6c0490eaf1119774ba9 onbuild
```