Fix a number of memory issues.

index.js
  -Convert the `addressStream` `CombinedStream` to an object
  containing multiple `CombinedStream`s, each of which is reserved
  for a different dataset.
  -Fixes an `DelayedStream#maxDataSize of Infinity bytes exceeded`
  exception that was being thrown.
  -Add TIGER Shapefile streams via a deferred callback, because
  the `shapefile` library wasn't playing well when multiple read
  streams were created and inserted into the TIGER
  `CombinedStream` one after the other.