Added How to Install Dependencies + Common Issue Section to README.md

[m-lin1]

Added a section on how to install the dependencies listed in the Dependencies section for people unfamiliar with Python dependency installations. Also added a section about common issues and how to solve them. These include how to revert back to a previous commit if Theano isn't working properly, as well as 2 other issues I ran into that I believe others might run into as well.