remove trailing comma from enum

makes being included from something with -std=c89 happy
Implement interface that provides the ability to have an outbound evhttp_connection free itself once all requests have completed
Add test for evhttp_connection_free_on_completion
Prevent duplicate event_del on fd
Merge remote-tracking branch 'origin/pr/180'
Merge remote-tracking branch 'origin/pr/182'
Start on 2.1.5-alpha/beta changelog