Rename Problem to Translation

app/models/problem.rb

@@ -1,10 +0,0 @@
-class Problem < ActiveRecord::Base
-  validates :title, :content, presence: true
-  validates :title, uniqueness: true
-
-  self.per_page = 50
-
-  def original_url
-    "https://projecteuler.net/problem=#{id}"
-  end
-end