Multiple word text formatting does not work for _, __, ___, etc.

[brycelelbach]

Multiple word text formatting using underscores instead of asterisks doesn't work properly. This is important to me because I need to write my markdown in a way that is mostly compatible with TWiki syntax, and TWiki and Markdown happen to share __ as a syntax for denoting important text (it's bold for Markdown, and bold with italics for TWiki).

I'm using Notepad++ v7.5.8 and markdown-plus-plus 81a86b4.

[SmashManiac]

From the readme:

_em text_, __strong text__ and ___em strong text___ only parse the first word because it will screw up some URL contains example__url.

Merge conflicts aside, does the proposed merge request #47 resolve this concern?