Fix some string encoding issues with entity bodies in HTTP requests.

RFC 2616 says that iso-8859-1 is the default charset for HTTP entity
bodies, but we encoded strings using ascii.  See
http://bugs.python.org/issue5314.  Changed docs and code to use
iso-8859-1.

Also fix some brokenness with passing a file as the body instead of a
string.

Add tests to show that some of this behavior actually works.
3 files changed