Parse completes w/o registered 'entry' listeners

Parse automatically consumes (and throws away) the same bytes that would
be piped through to an entry stream even when no 'entry' listener has
been registered. Otherwise entry streams fill up their buffers and can
cause #20.
Test Parse w/o registered 'entry' listeners
Add function to auto consume unwanted entries

Adds entry.autodrain() method which should be called on entries
that are not piped or read() from. Otherwise entry streams fill
up their buffers and cause #20.