Build, setup, and interpose on Date

The current public interface is through a global `Reanimator` symbol, which
provides the following:
* `Reanimator.capture` - interpose on non-deterministic methods (only Date
  implemented so far and start logging
* `Reanimator.flush` - return a clone of the current log as a JS object
* `Reanimator.cleanUp` - undo interposition on non-deterministic methods and
  return normal native implementation

Run tests with `make test`.