Changed Yahoo! to Yahoo.
Merge pull request #1262 from zhouyaoji/yhoo_icon_cleanup

[docs] Changed Yahoo! to Yahoo.
fixed sending error twice when another middleware already sent the headers
Merge pull request #1264 from jarnoux/master

better output handler response header check
update history file
Merge pull request #1265 from lzhan/history

update history file, add entry for pr #1264
Merge branch 'develop' into doc_exs_models
Changed model name from 'foo' to 'model'.