Fixes # 2172
Merge pull request #2223 from czpython/fixes-2172

Fixes # 2172
Added missing django.db.models import to docs
Merge pull request #2230 from dbrgn/docs_import_fix

Added missing django.db.models import to docs
Unicode fix to make Sphinx 1.2b2 happy
Merge pull request #2233 from yakky/feature/unicode_fix_docs_test

Unicode fix to make Sphinx 1.2b2 happy
Fix placeholder documentation
Fix another paragraph
Documentation revision. Thanks @mkoistinen
Merge pull request #2249 from yakky/feature/ph_docs

Fix PlaceholderField documentation