Proposed solution for Issue #104: multiple cookies

Patch so that the _parse_headers function handles multiple cookies by appending them, separated by a comma and space. See lines 361-364. This mimics the behaviour of Python requests when it comes to response.headers['set-cookie'] and response.headers.items().

Currently this function just writes over any previous cookie, leaving only the last one. 

Thrilled to be submitting my first public pull request. Thanks to @askpatrickw and @tekktrik for their encouragement.

Author: MarkTsengTW

adafruit_requests.py

@@ -358,7 +358,10 @@ def _parse_headers(self) -> None:
                     self._remaining = int(content)
                 if title == "transfer-encoding":
                     self._chunked = content.strip().lower() == "chunked"
-                self._headers[title] = content
+                if title == "set-cookie" and title in self._headers:
+                    self._headers[title] = self._headers[title] + ", " + content
+                else:
+                    self._headers[title] = content
 
     def _validate_not_gzip(self) -> None:
         """gzip encoding is not supported. Raise an exception if found."""