Remove hard_wrap option

I try to limit all lines in markdown files to 80 characters.

Unfortunately, with the `hard_wrap` option, `<br>` tags are inserted for all new lines, which is not the default Markdown behavior ([see doc](https://github.com/vmg/redcarpet#darling-i-packed-you-a-couple-renderers-for-lunch)).

Here is an exemple of a [README](https://raw.githubusercontent.com/odolbeau/cookbook-statsdaemon/master/README.md) with [a pretty bad renderer](https://supermarket.getchef.com/cookbooks/statsdaemon).