RF: use pyo.Server if it has its own __del__ (pyo v0.6.4+)
RF: fMRI emulator issue with simulated responses under pyglet 1.2alpha

- was getting timing errors in fMRI_launchscan demo when using pyglet 1.2alpha
- deleting the simulated participant key-presses fixed the demo (simplified it too)
- defer a proper fix until after iohub is integrated
Merge pull request #292 from jeremygray/master

fMRI sync emulator fix