Merge pull request #326 from minrk/checkrc

inline _check_rc for cython backend

pure Python calls were expensive
also cleanup a few libc cimports
rc3
add select to API doc

and cleanup some rst formatting
add `__dir__` to context and socket

allows completion on sockopts in places like IPython.
Currently only completes uppercase sock opts,
even though lowercase sock opts work.
fix version check in test_dir
Merge pull request #328 from minrk/cleanup

allow completion on sockopt names
rst underline fixes
Configure inherits from build_ext, not build

otherwise it can get the wrong compiler (e.g. mingw)
remove insurance industry
release 13.0.0
back to dev
minor sphinx fixes
fix device headers
Fixed just zmq detection
Merge pull request #329 from xantares/master

fixes librt detection / linking on Linux.

closes #329
Update XREQ to DEALER and XREP to ROUTER
Merge pull request #334 from stuaxo/master

Update XREQ/XREP to DEALER/ROUTER in gevent example.
add version-checking for Cython

better warnings for users of too-old Cython.
don't turn EINTR into KeyboardInterrupt

This is redundant, and ends up doing the wrong thing when a signal handler is registered for SIGINT.
Merge pull request #336 from minrk/oldcython

add version-checking for Cython

better warnings for users of too-old Cython.

closes #335