Improve reporting on user errors about bananas-frontend-cli

[erenes]

I've fixed this specific issue in the commit mentioned above, but I based it on a branch already containing my PRs #20, #21 and #22.

There will be some merge conflicts if we merge them one by one, so before sending a PR for this, I wanted to check if it would be better to send a new PR that combines all the fixes in one PR, or would you rather merge the other PRs first and then have me rebase off that?

[TrueBrain]

What I commonly do, is make the PR with the others included, and stating that in the Pull Request (something like: include #.., #.., etc). That means for the reviewer it is clear in which order he should review the stuff, and makes sure you don't have to make your life very complicated :D

Also poke to reviewers to get a move on :P