Add in support for Django 5.0 by adding in compat functionality for datetime_safe

[chander]

This change adds in support for Django 5.0 in Tastypie by doing the following:

1. Add in a compatability function.
2. Update the tests to properly indicate the versions of python and django suitable for testing with this release.
3. Ensure that tox tests pass properly.

Running Sphinx v7.2.6
making output directory... done
building [mo]: targets for 0 po files that are out of date
writing output...
building [doctest]: targets for 51 source files that are out of date
updating environment: [new config] 51 added, 0 changed, 0 removed
reading sources... [100%] who_uses
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
running tests...

Document: cookbook

1 items passed all tests:
16 tests in default
16 tests in 1 items.
16 passed and 0 failed.
Test passed.

Doctest summary

16 tests
0 failures in tests
0 failures in setup code
0 failures in cleanup code
build succeeded.

Testing of doctests in the sources finished, look at the results in ../tmp/html/output.txt.

[coveralls]

coverage: 94.303% (+0.03%) from 94.274%
when pulling e213f6d on chander:master
into 88e0218 on django-tastypie:master.

[chander]

@georgedorn can you please review and merge to add Django 5.0 support to tastypie? Thanks

[chander]

@georgedorn should be good to go now -unless you have other changes?