Report verbosity

[ev-br]

Implement several verbosity levels:

• no output, failures only
• dots for objects
• names of objects
• full, from doctest's -v

Also this need to work with both stdout/stderr redirected and not.

[ev-br]

While at it, reproduce the niceties of refguide-check

[ev-br]

gh-31 adds three verbosity levels, maybe that's enough. Since this is user-facing, maybe add string aliases to numerical levels (e.g. verbosity="minimal" vs verbosity=0), but that for a follow-up, if at all.

[ev-br]

.... F.... does seem to be useful for tutorials, after all. a tutorial is a single test with 100s of examples.