Flask-cors

Updated logging.warn to logging.warning (234) Thanks Vaibhav

Manual error in release process. Identical contents at 3.0.5.

Fixes incorrect handling of regexes containing `[`, and a few other special characters. Fixes Issue [212](https://github.com/corydolphin/flask-cors/issues/212)

Handle response.headers being None. (Fixes issue 217)

Ensure that an Origin of '*' is never sent if supports_credentials is True (fixes Issue 202)
* If `always_send=True`, and `'*'` is in the allowed origins, and a request is made without an Origin header, no `Access-Control-Allow-Origins` header will now be returned. This is breaking if you depended on it, but was a bug as it goes against the spec.

Fixes Issue 187: regression whereby header (and domain) matching was incorrectly case sensitive. Now it is not, making the behavior identical to 2.X and 1.X.