doc: add documentation for try_send and update docs for try_write
test: add a missing close() for socket

This suppresses a ResourceWarning in Python 3.5alpha
core: fix refcount bug in func_excepthook()

Found with python compiled with --with-pydebug.
core: fix access of potentially freed memory

Found with python compiled with --with-pydebug

saghul: if the PYUV__PYREF flag is set then it's guaranteed that the
object has a refcount >= 2. If the the flag is not set, however, it's
possible that we arrive here with a refcount of 1, then the first
Py_DECREF would free the object, and immediately after we'd check the
flags of such dead object.

I guess this never blew up IRL because nobody overwrites the memory, but
when running with a debug build, memory is overwritten, precisely to
help catch this kind of bugs. Nice catch @geertj!
build: add Python 3.4 to tox and remove 3.0-3.2 from classifiers

Python 2.6, 2.7, 3.3 and 3.4 are the Officially Supported Versions (TM).
One of these days I might drop support for Python 2.6. Because Future
(TM).