don't import gc thread more than once

should close #425
Merge pull request #426 from minrk/gc

don't import gc thread more than once
update version_info

semver-style always 3 ints, dev is 4th entry, if any
pass on utils docs
monitor fixup
pass on core zmq docs
pass on device docs
index pass
import zmq for docs version
changelog for 14.0
update version test
restore deprecated aliases
update perf.py