Ability to serialize RAM / frame buffer when cloning states

Currently, the ALE doesn't serialize the RAM or frame buffer when cloning states. There are various issues with naively doing this (see #413) but there are potential workarounds.

1. Add a flag to optionally serialize both RAM/frame buffer.
2. The emulator is now deterministic so we could serialize the state at the time `t-1` and run the emulator forward one frame which would rehydrate both the RAM and frame buffer. The logic of this could get messy but it would be easy to remain backwards compatible.

I believe upstream Stella has this functionality now so it might be worth taking a look to see how they managed this.