http://qiita.com/tomtoma/items/84479d7dde6e1bc18c5a

Preferences > Key Bindings - user を開いて下記コードを流し込み

{ "keys": ["shift+enter"], "command": "insert", "args": {"characters": "<br />" } },
{ "keys": ["ctrl+enter"], "command": "insert", "args": {"characters": "<br>" } }