Implement server push, exposed as the HTTP20Push and HTTP20PushedResponse classes
Rename extract_from_key_value_set to pop_from_key_value_set, have it modify the set in-place
Temporarily revert addition of 'pushed' attribute from requests adapter Response object pending further discussion
Merge BaseHTTP20Response, HTTP20Response, and HTTP20PushedResponse for simplicity
Add more comments to critical paths in Stream
Rework the server push API to account for PUSH_PROMISEs that arrive after the original response headers
Add enable_push flag to HTTP20Connection constructor and cancel() method to HTTP20Push
Update/clarify push docs
Use HTTP20Connection._get_stream() in more places
Don't use single-item tuple deconstruction assignment for clarity
Revert remaining decorative changes to test_integration.py
Fix bug: util.get_from_key_value_set() shouldn't modify its arguments
More testing for stream canceling and Continuation handling
Merge pull request #40 from alekstorm/server-push

Implement server push