Update Aim version and add Aim running instructions on README

[SGevorg]

HI, Gev here - the author of Aim
Love your work on the NeoRL and would love to contribute.

Changes Proposal

Aim 3.x has been released a while ago and it's a much improved and better scalable version (especially for the RL cases).
Would love to update Aim to 3.x and add an instruction section on README so it's easier to run the benchmarks?

Motivation

To provide easy and smoother experience for the NeoRL users with Aim.

[mzktbyjc2016]

Thanks for your suggestion! Currently, we are working on other projects, and will soon update to Aim 3.x if the interface does not change too much.