#16 Uncovered source files.

implements Feature from issue #16

Off by default, but if someone wants it, they can just set show_uncovered_files to true in the config block.

Why aren't there tests?

I tried to write a few features to demonstrate the functionality but the way the test harness run it touches the uncovered source file and shows up in the coverage data.  So basically when I run the tests I can't recreate the issue.

If it's a big deal maybe I can spend some time in the future trying to work that up.