Use the Ruby Style Guide where practical

[derekpovah]

I'm doing more work on this gem and my Rubocop linter is constantly yelling at me. Would you accept a pull that starts to implement some of the best practices laid out in the Ruby Style Guide?

What are your thoughts about bringing Rubocop in as a development dependency? We can have a conversation about what we'd want this project's .rubocop.yml to look like if we move ahead with this.

Rubocop's current output:

36 files inspected, 1031 offenses detected, 722 offenses autocorrectable