Rescue on WikiCloth exception

[JuliusR]

See #229.

[wvengen]

Nice :) What about moving the alert classes into code (and remove html_safe)?

[JuliusR]

For me, the html_safe is essential because the rescue happens in the controller. Is it better now?

[wvengen]

Thanks, that's a bit easier on the translators 👍

[wvengen]

The error is a bit vague though, what about showing the actual error message? Perhaps something like: "I'm sorry to report that an error occured when interpreting the wiki page: %{msg}. Please try to fix it, and save the page again.".
(some wikicloth exceptions)

[JuliusR]

Yeah, I thought about that. However, since the error message for me does not allow to conclude about the problem, I did not implement it before. Here is my attempt.