Match its behavior in pyPersistence.

This makes the pure-Python implementation match the C version.

Fix copyright holder per repository policy.

Ensure that Python reference impl. of Timestamp gets tested even if C
impl. builds.

Zap fossil timestamp-manipulation functionss:  they now live in
'persistent.timestamp'.

Drop can't-get-here condition in PickleCache.__delitem__.

Cover PickleCache.debug_info, and fix a bug found thereby.

Drop support for Python < 2.6.

- Installs 'Sphinx' and 'repoze.sphinx.autointerface'.

- Installs 'nose' and 'coverage'.

Tests now run with 'setup.py test'.

```---------------------------------------------------------------------
r122975 | tseaver | 2011-09-27 13:31:54 -0400 (Tue, 27 Sep 2011) | 1 line

Move to match order defined in IPickleCache.
```

---------------------------------------------------------------------
r122974 | tseaver | 2011-09-27 13:31:06 -0400 (Tue, 27 Sep 2011) | 1 line

Tolerate being handed irrelevant arguments.
------------------------------------------------------------------------
r122973 | tseaver | 2011-09-27 13:31:05 -0400 (Tue, 27 Sep 2011) | 1 line

Enable 'Timestamp' fallback to 'timestamp' when extension unavailable.
------------------------------------------------------------------------
r122972 | tseaver | 2011-09-27 13:31:04 -0400 (Tue, 27 Sep 2011) | 3 lines

Don't raise KeyError for OID collision w/ same value object.

Also, implement stub of 'update_object_size_estimation'.
------------------------------------------------------------------------
r122971 | tseaver | 2011-09-27 13:31:03 -0400 (Tue, 27 Sep 2011) | 1 line

Document additional picklecache methods.

It is used only in the doctests.

Those snippets now pass with both the Python and the C versions of Persistent.