Updated markdown and cleaned up README.md

[billhance]

I cleaned up the formatting a little bit but feel free to ignore as I know this is an exercise on learning how to use git better.

Here is a rundown on changes:

• Changed name of file that contained the Backyard Loupe poem to better reflect what it contains.
• Added a CONTRIBUTING.md file. That's the standard way of communicating to potential contributors all the why, what, how, etc.
• Added some links and markdown for style purposes.