Delegate Base.exists? to Relation

We can use the Relation implementation of exists? and then delegate the
method on Base. This will give us one implementation that can be used on
but the record class or a scoped relation.

Author: michebble

lib/active_hash/base.rb

@@ -103,20 +103,6 @@ def data=(array_of_hashes)
         end
       end
 
-      def exists?(args = :none)
-        if args.respond_to?(:id)
-          record_index[args.id.to_s].present?
-        elsif !args
-          false
-        elsif args == :none
-          all.present?
-        elsif args.is_a?(Hash)
-          all.where(args).present?
-        else
-          all.where(id: args.to_s).present?
-        end
-      end
-
       def insert(record)
         @records ||= []
         record[:id] ||= next_id
@@ -190,7 +176,7 @@ def all(options = {})
         relation
       end
 
-      delegate :where, :find_each, :find, :find_by, :find_by!, :find_by_id, :count, :pluck, :ids, :pick, :first, :last, :order, to: :all
+      delegate :exists?, :where, :find_each, :find, :find_by, :find_by!, :find_by_id, :count, :pluck, :ids, :pick, :first, :last, :order, to: :all
 
       def transaction
         yield