Add original tracebacks when re-raising an exception from another greenlet

Also some greenlet module cleanups.

Fixes #450. Fixes #528.

Make JoinableQueue.join consistent when items are passed to the constructor, extending #554; add a test for this.

Note that Python 2.5 support has been dropped. Add version and implementation classifiers to setup.py; make setup.py PyPy/Py3 friendly and not leak open files. [skip ci]

Update config.guess and config.sub. Fixes #550. Fixes #532. Fixes #502.

Per discussion in #248, start writing more CFFI in C instead of Python. This commit gets the individual watcher callbacks into C

Cleanup some warnings in test__doctest.py (an unclosed file, an unknown string escape). Run doctests in a predictable order.

Provide some documentation for gevent.backdoor.BackdoorServer.

c-ares update

Fix Python 3 test failures. Thanks to the contributors of the following issues (at least): Fixes #412. Fixes #413. Fixes #416. Fixes #421. Fixes #462. Fixes #409.

Update the changes from #409 and merge them. Use this new FileObjectPosix to implement the socket._fileobject where possible. Fixes #409.

Better reflect the way leaktests are handled now; this should restore test__backdoor to its FLAKY status on Travis.

Python3 on certain platform (not OS X) raised 'ValueError: cant have unbuffered text I/O', so line buffer it.