Add trailing newline to markdown report

[rgryta]

Without trailing newline in a markdown report, the first additional information that comes from cmdline handler will end up in an additional row below the TOTALs row.

E.g. Coverage failure: https://github.com/nedbat/coveragepy/blob/master/coverage/cmdline.py#L761

[nedbat]

Will you be fixing the failing tests?

[rgryta]

Will you be fixing the failing tests?

Hi, yes. Haven't had time to work on them this weekend. I'll change the last_line assertions to second_last_line.
Unless they'd be better implemented in some other way? Like adding a deletion of all last lines that are empty before performing TOTALS line assertions?

I can add those changes in any way tbh.

[nedbat]

I think I'd change the last_line_squeezed function to return the last non-blank line. Line count assertions can be incremented.