Add support for configuring HTTP timeouts

Summary
Current http_open_timeout is set to 15 seconds, which is causing some issues with today's AWS Kinesis outage. Make this value and some other timeout values configurable

Other Information
Journaled.http_idle_timeout (default: 1 second)
The number of seconds a persistent connection is allowed to sit idle before it should no longer be used.

Journaled.http_open_timeout (default: 15 seconds)
The number of seconds before the :http_handler should timeout while trying to open a new HTTP session.

Journaled.http_read_timeout (default: 60 seconds)
The number of seconds before the :http_handler should timeout while waiting for a HTTP response.