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
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.
Generator implementation of class mapping.
Remove Login Dropdown when Auth Views are not registered.

Fixes #1738
Merge branch 'master' of github.com:tomchristie/django-rest-framework into login-dropdown
Fix docstring
Fix imports
Moved li tags inside `optional_login`

as per https://github.com/tomchristie/django-rest-framework/pull/1820#discussion_r16987993
Add custom pagination test that covers case with custom object serializer class
Use explicit many=True for object_serializer instantiation in PaginationSerializer and add catch dummy 'many' kwarg on DefaultObjectSerializer
remove rogue print
Merge pull request #1826 from swistakm/fix/explicit-many-in-pagination-serializer-results

Use explicit `many=True` in PaginationSerializer on `object_serializer` instantiation
Version 2.4.2