Multiline bold is not highlighted

[ghost]

Hi, thanks for the nice plugin. One thing I noticed

In Sublime Text:

__highlighted__

__not
highlighted__

In GitHub:
bold

multiline
bold

[jonschlinkert]

This works fine unless there is a hard line break. GFM does some things that require advanced parsing and are out of the scope of this plugin.

I'm going to close this since I don't see this as a bug, and the solution is to not do a hard line break in the middle of bold or italicized text. But I'd be happy to look at a pr if anyone wants to try to resolve this.