- core module gets a completely new interface, incompatible with gevent-0.13
- SystemExit, KeyboardInterrupt and SystemExit are now re-raised in the main greenlet
- Python's signal module works

__init__.py:
  - add get_hub to __all__
  - remove shutdown()

get_hub() now accepts arguments to pass the loop (e.g. get_hub('select'))

Hub class:

  - new methods: handle_error, wait, cancel_wait, join
  - removed method: shutdown (replaced by join())

Timeout class:

  - allow passing string as exception

coros, event, greenlet:

  - use hub's handle_error to report_error rather than traceback module
  - save hub as an attribute rather than calling get_hub() all the time

--HG--
rename : gevent/core.pyx => gevent/core_.pyx