Add anything-sage.

Thank you very much for the quick merging.

[anything-sage](https://github.com/stakemori/anything-sage) provides an [anything](http://www.emacswiki.org/Anything) source for [sage-shell-mode](https://github.com/stakemori/sage-shell-mode).
This is an `anything` version of [helm-sage](https://github.com/stakemori/helm-sage).

I am the author and the maintainer of [anything-sage](https://github.com/stakemori/anything-sage).

Please merge this pull request.