Add rubocop.
Rubocop: use the new Ruby 1.9 hash syntax.
Rubocop: prefer single-quoted strings.
Rubocop: add spaces around braces.
Rubocop: add surrounding space.
Rubocop: use parens for word lists.
Rubocop: align method arguments.
Rubocop: space between ! and its argument.
Rubocop: remove empty lines at body beginning.
Rubocop: use && instead of and.
Rubocop: space missing after comma.
Rubocop: split long lines.
Rubocop: File.exists? is deprecated.
Rubocop: prefer fail to raise.
Rubocop: fixes for indentation.
Rubocop: align case statements.
Rubocop: use || instead of or.
Rubocop: use parens for %Q literals.