v0.4.2

With this release, @amasad and I fixed a bug with exploded for-in loops that was reported by @qfox (#90). Inherited (non-own) object properties were being skipped by such loops, and properties deleted during a loop could sometimes be visited later in the loop. As a bonus, the code generated for exploded for-in loops is now less verbose than before, with more of the key-iteration logic now residing in the runtime!