tests: Add hspec to build-depends
tests: Fix build
Add udev rules
Fix build with aeson >= 0.7.

It removed ByteString instances (https://github.com/bos/aeson/issues/126)
cabal: Require optparse-applicative >= 0.7.0
Hemokit.Start: Fix selecting a real EEG with --serial.

We had to choose the last device in this case as well.
hemokit-mouse: Use the last device