adds Budget::Group model to group headings

many refactors through budget related models

db/migrate/20160520111735_create_budget_heading.rb

@@ -1,9 +1,9 @@
 class CreateBudgetHeading < ActiveRecord::Migration
   def change
     create_table :budget_headings do |t|
-      t.references :budget
+      t.references :group, index: true
       t.references :geozone
-      t.string     :name, limit: 50
+      t.string :name, limit: 50
       t.integer :price, limit: 8
     end
   end

db/migrate/20160609110023_create_budget_group.rb

@@ -0,0 +1,10 @@
+class CreateBudgetGroup < ActiveRecord::Migration
+  def change
+    create_table :budget_groups do |t|
+      t.references :budget
+      t.string     :name, limit: 50
+    end
+
+    add_index :budget_groups, :budget_id
+  end
+end

db/migrate/20160609142017_remove_price_from_budget.rb

@@ -0,0 +1,5 @@
+class RemovePriceFromBudget < ActiveRecord::Migration
+  def change
+    remove_column :budgets, :price, :integer
+  end
+end

db/migrate/20160609152026_remove_budget_id_from_investments.rb

@@ -0,0 +1,5 @@
+class RemoveBudgetIdFromInvestments < ActiveRecord::Migration
+  def change
+    remove_column :budget_investments, :budget_id, :integer
+  end
+end