update decode w.r.t. safe !!
  - Note `sequence [Just 1]` is OK but `sequence $ [Just 1] is not`.
    See purescript/issues/376.
checkpoint... making progress with purescript and reactive
checkpoint again. current error is:

>> Error at src/footpedal_vp.purs line 42, column 30:
>> Error in declaration service
>> Cannot unify [Footpedal.PedalState] with Ws.Packet.
checkpoint: compiles without errors, with most of the guts commente out
service compiles, if I comment out the type decl
The field names for effects have to match!
restored some type decls
updated build deps; started adding stuff to README.md