Refactor BannerRequests to prevent unclosed connection warnings

[gannonprudhomme]

We need to refactor the BannerRequests module to use a different system for creating Session objects, as we get a plethora of Unclosed Connection errors.

One way that might prevent this if we create a fixed amount of sessions (I believe the max is 100) and used a bounded buffer / blocking queue to retrieve sessions after they are used, with a producer-consumer model (which was taught in CSCE 313).

I don't think the Unclosed connections warnings are a problem right now, but it would be nice if we could avoid them altogether.