fixes booth-poll relation

app/models/poll.rb

@@ -1,6 +1,6 @@
 class Poll < ActiveRecord::Base
-  has_many :booth_assigments
-  has_many :booths, through: :booth_assigments, class_name: "Poll::BoothAssignment"
+  has_many :booth_assignments, class_name: "Poll::BoothAssignment"
+  has_many :booths, through: :booth_assignments
   has_many :voters, through: :booths, class_name: "Poll::Voter"
   has_many :officers, through: :booths, class_name: "Poll::Officer"
   has_many :questions

app/models/poll/booth.rb

@@ -1,11 +1,11 @@
 class Poll
   class Booth < ActiveRecord::Base
-    has_many :booth_assigments
-    has_many :polls, through: :booth_assigments
+    has_many :booth_assignments, class_name: "Poll::BoothAssignment"
+    has_many :polls, through: :booth_assignments
     has_many :voters
     has_many :officing_booths, dependent: :destroy
     has_many :officers, through: :officing_booths
 
-    validates :name, presence: true
+    validates :name, presence: true, uniqueness: true
   end
 end