feature: Paragraph.add_text()

[etfre]

Right now, the quickest way to add text to the last run of paragraph p (preserving formatting/styles, versus p.add_run()) is through p.runs[-1].add_text(), which doesn't look particularly clean. I know that Texts aren't children of Paragraphs, but p.add_text() is intuitive and I suspect that many people will try to call it when they first start using the library.

[scanny]

Mmm, good point Evan. I remember the MS API has a paragraph.add_text() method (spelled differently) which has that behavior. I think you're right. That way whatever the current formatting is will be extended.

I'll mark this as a TODO to complete before closing out the alpha.

[scanny]

Pull request #71 implements this.