Added: undercover.el recipe

Hi!

I'm author of new library [undercover.el](https://github.com/sviridov/undercover.el) that provides a test coverage check for Emacs packages.

It's not very flexible right now and assumes a certain development cycle of your package (using [Cask](https://github.com/cask/cask), [ert-runner](https://github.com/rejeep/ert-runner.el), [Travis CI](https://travis-ci.org/) and [Coveralls](https://coveralls.io/)). But it's matter of time.

Here some examples of usage:

- Emacs-Elixir ([commit](https://github.com/sviridov/emacs-elixir/commit/df59e0a2e91cb9864fe01a790660fe980dfdfbf4), [report](https://coveralls.io/r/sviridov/emacs-elixir))
- Clojure Mode ([commit](https://github.com/sviridov/clojure-mode/commit/aaddbf492b6d145fbd9e31d766c0e787ab8c7222), [report](https://coveralls.io/r/sviridov/clojure-mode))
- undercover.el ([report](https://coveralls.io/r/sviridov/undercover.el))

Screenshots:

![1](https://cloud.githubusercontent.com/assets/1789390/4490597/14a2dc0e-4a2e-11e4-9816-5ca256dac7a4.png)
![2](https://cloud.githubusercontent.com/assets/1789390/4490598/14a34176-4a2e-11e4-97c4-e030db708c98.png)
![3](https://cloud.githubusercontent.com/assets/1789390/4490599/14a3e720-4a2e-11e4-9a07-b09450aa3c20.png)

Thanks!