Do not add pending cases to qfl?

[blueyed]

With #183 I've added a "Failure summary" section, which basically displays the qfl with errors in the terminal.

However, this also includes pending cases (prefixed with TODO/FIXME).

I wonder if having those in the quickfix list (also used when using Vader interactively in Vim itself) is good in general, or if this could just be changed to not add them there already?
I do not think they should be displayed in the failure summary at least, so would have to be filtered out there then.