Built `git annex testremote` today. 

That took a little bit longer than expected, because it actually found
several fence post bugs in the chunking code.

It also found a bug in the sample external special remote script.

I am very pleased with this command. Being able to run 640 tests against
any remote, without any possibility of damaging data already stored in the
remote, is awesome. Should have written it a looong time ago!
