Add tax_references, its controller and some basic pages for viewing ref data about taxes.

app/controllers/tax_references_controller.rb

@@ -0,0 +1,10 @@
+class TaxReferencesController < ApplicationController
+  def index
+    @tax_references = TaxReference.all
+  end
+
+  def show
+    @tax_references = TaxReference.all
+    @tax_reference = TaxReference.find_by(year: params[:year])
+  end
+end