Update argument usage via command line.

- Change argument usage and check if set.
- Add static usage method.
- Update readme usage sections.
Add comments using TomDoc spec.
Add exception handling when requesting URL.

- No need to initialize variables due to Ruby scoping.
- Add spacing lines for readability.
Refactor for better modularity.

- Add Schedule class to encapsulate connecting and receiving the data.
- Create new Schedule instance from static console method.
Refactor mlb-schedules.rb into separate files.

- Move schedule class into own file.
- Move console and constants into base file.
- Change main file to handle requiring needed files.
Move constants into globals file.
Use require_relative instead of require with current dir.
Return URL response instead of printing.

- Let console method handle the response from the URL request.
- Set URL during class initialization instead of when making the request.
Check for valid parameter values.
Add parsing and Game model class.

- Add Game model class.
- Add parse_csv method to Schedule class to handle reading each line and creating Game objects.