Evaluate content before passing to regex.sub

Issue #1708
evaluate content at function start
remove dep on python_2_unicode_compatible

python_2_unicode_compatible is not available in all Django versions
replace unicode call with force_text
Fix typos in 2.4 release notes
Fix links in 2.4 release
Update README.md
Restore body block to base template.
Exclude the pyc, pyo files and __pycache__ directories from packaging (thanks to Kevin Brown).
Merge pull request #1812 from linovia/bugfix/1804

Fix #1804
Merge pull request #1810 from danielroseman/restore-body-block

Restore body block to base template.
Regression for #1810: Test login view renders
Version 2.4.1
Comform to flake8
Merge pull request #1816 from carltongibson/regression-login-template

Regression for #1810: Test login view renders
Correct testing documentation details.
Merge pull request #1817 from tituomin/testing-requirements-documentation

Correct testing documentation details.
Add subclass matching to serializer field mapping.
Traverse the method resolution order when mapping serializer fields.
Add utility function to match classes in dictionary.