Ensure that all lines of underscores have at least two preceding newlines

[ndbroadbent]

Some users may reply directly above a line of underscores, because the gap between lines can be a little misleading, e.g.

Outlook with a reply directly above line
________________________________________
From: CRM Comments [crm-comment@example.com]
Sent: Friday, 23 March 2012 5:08 p.m.
...

Unfortunately, the parser cannot split fragments without empty lines between them.

This pull request solves that problem by ensuring that all underscore lines are preceded by at least two newline characters. (I can't think of any situation where that would cause a problem.)

The previous example will be 'pre-processed' into:

Outlook with a reply directly above line

________________________________________
From: CRM Comments [crm-comment@example.com]
Sent: Friday, 23 March 2012 5:08 p.m.
...

But if this ^ is run through the parser, it will not be affected.

[ndbroadbent]

Hi there, just wondering if someone might be able to take a look at this pull request?

Cheers!

[Intrepidd]

Great stuff, you saved my life :)

+1 for integration, but sadly this project seems a little bit inactive ..

[inspire22]

Please accept this :)

[Intrepidd]

🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉