Fix ruby `super_call` snippet

There was no tab in the beginning of the line and snippet wasn't
working.

Edit: update to explain the problem in more details.
I'm on vim 7.4, using snippets with [vim-snipmate](https://github.com/garbas/vim-snipmate).
When I'm in a ruby file, all ruby snippets work fine. However, `super_call` does not work. I investigated a bit and it turns out `super_call` snippet had only spaces before the template (instead of a tab). This pull request fixes that.