Added jrnl formula

Hi there, 

I added a new formula for [jrnl](http://maebert.github.io/jrnl/) following your `contributing` guidelines.
It installs on a mavericks host and runs the test correctly.

If possible, please merge.

Thanks for your work.
That makes sense, I don't know about the key saving (how persistent it is) or if it interacts with osx keyring (which I think it does). But I'll talk with jrnl maintainer.