Write literature review

[scowan1995]

@simofoti I will list the papers I am going to read so we don't accidentally overlap.

• Deep Reinforcement Learning for Sponsored Search Real-time Bidding by Jun Zhao et al. ArXiv 2018.
• A Survey on Real Time Bidding Advertising by Yong Yuan. Service Operations and Logistics 2014.
• Real-Time Bidding with Multi-Agent Reinforcement Learning in Display Advertising by Junqi Jin et al. ArXiv 2018.

May add more while working on other questions if I need to do research. If I add more I will update here