First Dino Dex Program

I have it set up right now to just run the code in the Main class, and it prints the results to the console.
It's actually possible to make this `attr_accessor` and just override the `weight_in_lbs=` method. It may seem like wasted work, but the use of `attr_reader` here appears to imply a domain rule (weight isn't settable) that isn't true. It's not a big issue, but it is definitely better to make it an accessor.