Section parser: Newlines in content can insert double spaces

[kevinansfield]

Discovered when copy/pasting using Firefox.

If parsed HTML contains newline characters, eg: (trailing spaces indicated with _ for easier visibility).

More of us have come to understand that our digital technologies are not
 always bringing out our best natures. People woke up to the fact that_
our digital platforms are being coded by people who don’t have our best_
interests at heart. This is the decade when, finally, the “tech_
backlash” began.

Then the generated mobiledoc can contain double spaces, eg:

"More of us have come to understand that our digital technologies are not  always bringing out our best natures. People woke up to the fact that  our digital platforms are being coded by people who don’t have our best  interests at heart. This is the decade when, finally, the “tech  backlash” began."