Don't ignore the help_type parameter

[Sharpie]

When helpr is loaded, it provides a new default method for:

print.help_files_with_topic

Currently, this method always serves HTML help, even if a user provides a different argument to the help function such as help(..., help_type = 'text').

This patch fixes this behavior by calling back to utils:::print.help_files_with_topic if the requested help type was something other than 'html'.

[hadley]

Good idea, but I think it would be better to return early, right after the type is determined, and skip all of the unnecessary code.

[Sharpie]

Commit amended.