Updated README.md (added Installing information, contribution instructions, unit testing instructions)

[RohanBha1]

This change adds information regarding how to install, contribute to, and perform unit testing on the project. It also fixes many markdown errors with the original documentation and reformatted the README to be easier to read and have a more logical flow of information. Some additional simple examples on using the project were added to not intimidate new users with the much more advanced examples included in the original documentation. Finally, a table of contents was added, as the documentation had gotten quite long so I thought this would improve accessibility.