Fixed #23725 -- Substituted AUTH_USER_MODEL for User in docs.
Fixed #23575 -- Added a code example for custom AdminSite.
Added missing imports to example from previous commit.
Fixed #23558 -- documented slugify limitations
Updated FIRST_DAY_OF_WEEK for Ukrainian to Monday.
Fixed #8149 -- Made File.__iter__() support universal newlines.

The following are recognized as ending a line: the Unix end-of-line
convention '\n', the Windows convention '\r\n', and the old
Macintosh convention '\r'.

http://www.python.org/dev/peps/pep-0278

Thanks tchaumeny for review.
Fixed #23468 -- settings.FIXTURE_DIRS checks in loaddata command