Initial Processing sketch for muon lifetime
Added an explicit open() method to FtdiChip
Cleaned up and further isolated unit tests

Yes! I fixed a few tests and the setup code.  Now, the tests do not even
depend on correct __init__ behavior.  If I break __init__, only *one* test
fails.  The other tests still verify the rest of the code.
Renamed flush_device() to flush() in FtdiChip
Test open() on unopened device, and only open once

Moved open() tests to another TestCase.
Added closed attribute to FtdiChip