Print the file name in the summary reporter if there is no context

[gaborcsardi]

The summary reporter is not bad in test_check(), for now. But w/o context(), I only get dots and it would be nice to get the file names in this case.

[hadley]

This is a quick fix — you won't get great results if you're still using context(); but I doubt that will affect many people, so I just did the minimum.