Chorde

Bugfixes
- Allow sPickle to accept strings as checksum keys, automatically
encode them as UTF8 to get byte keys, as most people would expect
string keys to work.

Bugfixes
- Fix empty reason field when re-raising tornado.web.HTTPError

Bugfixes
- Various string encoding fixes

Removed
- Dropped Python 2.x support

Added
- Added Python 3.6+ support

Changes
- Renamed fn.async() decorator call into fn.bg() to make it
Python 3 compatible
- Renamed clients.async module to clients.asyncache
(to make it Python 3 compatible)
- Key/value picklers now **must** return bytes
- Key/value picklers are now strategy instances instead
of namespaces. Check the new interface when migrating
code that passes custom picklers. New picklers must implement
the appropriate BasePickler subclass.
- Futures no longer strip exception tracebacks by default.
This follows Python 3's new traceback handling behavior,
but it may cause additional memory leaks due to the way
tracebacks hold references to frames and all local variables.
It is recommended that stripping is re-enabled for production
code using `chorde.clients.asyncache.set_strip_tracebacks(True)`.

Removed
- Lock pools and deadlock detection from chorde.serialize have
been removed (no longer used)

Bugfixes
- Fixed high latency (50ms) of missing `async()()` calls
- Fix alternative slot search in SharedCounter when the autoselected
slot is occupied.

Bugfixes
- Apply TTL namespace variation on all code paths.
Some were neglected.