Bug fix: PartialCallsComponent doesn't pass object_ids to ValueComponent
Bug fix: wasn't passing third parameter to BytecodeSpool.
Added levels to topics, and showing them.  Also hide the exercise box if the corresponding exercise doesn't exist.
Bug fix: gets call stopped working.  Ripped out $stdin_is_waiting while I'm at it.
Interpreter now supports block parameters (no yield yet though).
Now interpreter supports yield.
Bug fix: e.cause was missing backtrace for ArgumentError.
Interpreter now supports while loops and Array#each.
Bug fix: blocks with only one statement in them didn't get a [:position] at front, so debugger wouldn't stop before executing that line.