Don't force a trailing newline after paragraphs

This fixes the following test case, which introduced dirty diffs in VE edits
on simple pages:

echo -n '<p>a</p>' | node parse --html2wt

No changes in parserTests.

Change-Id: Ia52dd8b9a7a6d0f10bedc1c70291b2f7a6a19274
TODO: Add tests without trailing newlines (if possible)
Merge "Don't force a trailing newline after paragraphs"