Simplified code

* Spread out really long initialization
	1. apps/models/challenge.rb
* Changed `[]` to `%w()`
	1. app/models/rating.rb
	* Note: %w() is a shortcut for declaring an array with only strings
* Converted oneline `do-ends` -> `{}`
	1. apps/models/round.rb
* Changed Array initialization: `[]` -> `Array.new`
	1. apps/models/round.rb
* Removed excess ()s
	1. app/models/round.rb

Signed-off-by: Zachary Perlmutter <zrp200@gmail.com>