fdb.py 0.5: get becomes show

I've done a bit more to fdb.py. It's mostly tidying up and more tests (you can never have enough tests!), but there's a significant change to the command line interface: I've changed the get command to show. So now, you'd type something like:

  fdb show -a DADGAD /njr/rating

instead of

  fdb get -a DADGAD /njr/rating

That assumes you have an alias or shell script pointing at it, of course. If not, the full thing is:

  python fdb.py show -a DADGAD /njr/rating

The reason for the change is that (somewhat reluctantly) I've concluded that it's going to be useful to support raw HTTP GET, POST, PUT, DELETE and HEAD for lower-level stuff, and it seems cleaner if those commands are just of the form

  fdb get whatever

There are other minor changes; see the log. And I added a nice, permissive license ("stolen" from Nicholas Tollervey; but I don't think he'll mind).