Use django.contrib.staticfiles instead of django-staticfiles.

cms/envs/bok_choy.py

cms/envs/common.py

cms/envs/devstack.py

cms/envs/devstack_optimized.py

cms/envs/test_static_optimized.py

common/djangoapps/pipeline_js/views.py

...on/djangoapps/pipeline_mako/templates/static_content.html

common/djangoapps/static_replace/__init__.py

common/djangoapps/terrain/browser.py

docs/en_us/platform_api/source/conf.py

lms/djangoapps/branding/__init__.py

lms/djangoapps/branding/api.py

lms/djangoapps/branding/views.py

lms/djangoapps/courseware/tests/test_comp_theming.py

lms/djangoapps/verify_student/views.py

lms/envs/bok_choy.py

lms/envs/common.py

lms/envs/devstack.py

lms/envs/devstack_optimized.py

lms/envs/test_static_optimized.py