tests: don't leak sockets
tests: socketpair() in 2.X is different...
cosocket: keyword args for makefile()
Merge branch 'master' into python3

* master:
  cosocket: keyword args for makefile()
  tests: socketpair() in 2.X is different...
  tests: don't leak sockets
  coserver: sockets recv()
  tests: rewrite and expand cosocket test with unittest
  also clear HTTP_PROXY for cosocket test

Conflicts:
	cothread/cosocket.py
	tests/cosocket.py
in python 3.x socket() and socketpair() both create the same thing