add irony-mode and company-irony recipes

I'm the author or [irony-mode](https://github.com/Sarcasm/irony-mode) and [company-irony](https://github.com/Sarcasm/company-irony).

I'm submitting both package at the same time since they are related to each other.

* The first package `irony-mode` provides a minor-mode that enhance the C/C++ coding experience in Emacs.
* The second package `company-irony` provides a `company-mode` completion backend for irony-mode.