NF: class SpooledEphemeralFile

- try to keep everything in RAM (so if RAM swaps out to disk, its encrypted)
- smooth out readlines() recursion issue
- require a 256-bit key
- probably inefficient implementation, readlines is slow
- a few minimal tests
Merge branch 'master' into class-SpooledEphemeralFile

- want to get tests (so can add SpooledEphemeralFile tests)

* master:
  Added unit tests
TESTs: convert pytest to unittest for SpooledEphemeralFile
Merge pull request #2 from jeremygray/class-SpooledEphemeralFile

NF: class SpooledEphemeralFile