Bump version to 0.2next
Add safeguard against pool sharing among processes

Forking the process will copy the pool's semaphore
allowing uncontrolled shared access between the processes.
add test for process sharing guard
clear http pool registry in init_http_pooling()

This is useful when forking a new process,
where old pools cannot be shared and must be discarded.
Add a caller-supplied component to http pool keys

The http pool module offers a default pool registry
as a convenience so that callers don't handle pool creating
and registering. However this pool was unconditionally global,
each pool identified by (scheme, network location).
Thus several modules connecting to the same server within the same
python interpreter would necessarily share the same pool.

This was amended by the introduction of a pool key, making
each pool identified by (pool key, scheme, network location).

The pool key is optional, and if not given a default is used,
recreating the previous global pool sharing.
Fix tests
fix crash in pool_get(create=False)
remove debug print in tests
Merge branch 'develop'

Conflicts:
	version