With upcoming ZODB 5, oids (used as persistent references in pickles)
are no longer str as it use to be with ZODB 4, but instances of
zodbpickle.binary, which with zodbpickle 1 are a subclass of str on
python2.

OrderedPickler was a subclass of pickle.Pickler, the pickler from standard
library, but this pickler was not able to use a str subclass for persistent
references, when pickles are loaded with noload method, persistent_load
is called with `None` instead of the actual string subclass instance.
This was problematic in the XMLExportImport handling of business templates,
because ZODB.serialize.referencesf was unable to find persistent references.
The error was:

    ZODB-5.6.0-py2.7.egg/ZODB/serialize.py", line 664, in referencesf
        assert isinstance(reference, list)
    AssertionError

because the reference was None.

zodbpickle 2 changed to make zodbpickle.binary implemented in C, which
was failing earlier, because pickle.Pickle can not pickle these objects,
failing in an error like this:

    lib/python2.7/copy_reg.py", line 70, in _reduce_ex
        raise TypeError, "can't pickle %s objects" % base.__name__
    TypeError: can't pickle binary objects

This change also simplify our own implementation, by dropping jython
support and calling save_dict on the super class instead of copying the
implementation.

Further references:

- minimal script to reproduce the issues:

```python
from __future__ import print_function
import io
import pickle

import zodbpickle
import zodbpickle.pickle
import zodbpickle.fastpickle

class ExternalObject(object):
  def __init__(self, oid):
    self.oid = oid

def persistent_id(obj):
  if isinstance(obj, ExternalObject):
    return obj.oid

def persistent_load(persid):
  print('persistent_load called with persid', repr(persid))

o = ExternalObject(oid=zodbpickle.binary("binary persid"))

for pickler_class in pickle.Pickler, zodbpickle.pickle.Pickler:

  f = io.BytesIO()
  p = pickler_class(f, 1)
  p.persistent_id = persistent_id
  p.dump(o)

  print('dump with pickler %s:\n  %r' % (pickler_class, f.getvalue()))

  # ZODB uses this unpickler
  up = zodbpickle.fastpickle.Unpickler(io.BytesIO(f.getvalue()))
  up.persistent_load = persistent_load
  up.noload()
```

```console
$ python2 repro.py # with zodbpickle 1
dump with pickler pickle.Pickler:
  'ccopy_reg\n_reconstructor\nq\x00(czodbpickle\nbinary\nq\x01c__builtin__\nstr\nq\x02U\rbinary persidq\x03tq\x04Rq\x05Q.'
persistent_load called with persid None
dump with pickler zodbpickle.pickle_2.Pickler:
  'U\rbinary persidq\x00Q.'
persistent_load called with persid 'binary persid'
```

```console
$ python2 repro.py # with zodbpickle 2
Traceback (most recent call last):
  File "repro.py", line 45, in <module>
    p.dump(o)
  File ".../lib/python2.7/pickle.py", line 224, in dump
    self.save(obj)
  File ".../lib/python2.7/pickle.py", line 273, in save
    self.save_pers(pid)
  File ".../lib/python2.7/pickle.py", line 340, in save_pers
    self.save(pid)
  File ".../lib/python2.7/pickle.py", line 306, in save
    rv = reduce(self.proto)
  File ".../lib/python2.7/copy_reg.py", line 70, in _reduce_ex
    raise TypeError, "can't pickle %s objects" % base.__name__
TypeError: can't pickle binary objects
```

* ZODB change starting to use zodbpickle.binary instead of str:
12ee41c4 (-ZODB now uses pickle protocol 3 for both Python 2 and Python 3., 2018-03-26)
Since of 5.4.0 release

* zodbpickle change starting to use C objects for zodbpickle.binary:
bbef98c (Implement zodbpickle.binary in C for Py27., 2019-11-12)
Since of 2.0.0 release