Fix of UnicodeDecodeError on unicode header name that can be converted to ascii.
removed no longer used redirect codes from models
added numeric values of redirect codes in comments
Deleted is_py2 check from unicode_header_name fix thanks to Lukasa.
Merge pull request #1184 from piotr-dobrogost/numeric_codes

small cleanup of redirect codes
Merge pull request #1181 from denis-ryzhkov/master

Fix of UnicodeDecodeError on unicode header name that can be converted to ascii.
Dispatch hooks before following redirects

Fixes #1183
Merge pull request #1185 from sigmavirus24/fix_hook_dispatching

Dispatch hooks before following redirects