v1.7.0

• Fixed memory leak via sys.last_type, sys.last_value,
  sys.last_traceback. Contributed by Anton Ryzhov in
  #59.
• Fixed a bunch of double-close bugs and simplified stream handler
  code. Contributed by Anton Ryzhov in
  #58.
• Loosen up pid argument parsing in manhole-cli to allow using
  paths with any prefix (not just /tmp).