Add migrations generator

db/migrate/1_create_media_objs_and_media_attachments.rb

+class CreateMediaObjsAndMediaAttachments < ActiveRecord::Migration[5.1]
+  def change
+    create_table :media_objs do |t|
+      t.attachment :file
+      t.string     :type
+      
+      t.references :creator, polymorphic: true
+      t.timestamps
+    end
+
+    create_table :media_attachments do |t|
+      t.string     :column_name
+
+      t.references :attached, polymorphic: true
+      t.references :obj
+      t.timestamps
+    end
+  end
+end

lib/generators/whaleback/migrations_generator.rb

+require 'whaleback/generators/migrations_generator'
\ No newline at end of file

lib/whaleback.rb

 require "whaleback/version"
+require 'paperclip'
 
 module Whaleback
   # Your code goes here...

lib/whaleback/generators/migrations_generator.rb

+require 'rails/generators/migration'
+
+module Whaleback
+  module Generators
+    class MigrationsGenerator < Rails::Generators::Base
+      include Rails::Generators::Migration
+      desc 'Copy whaleback migrations to your application.'
+
+      def self.next_migration_number(dir)
+        sleep 1
+        Time.now.utc.strftime("%Y%m%d%H%M%S")
+      end
+
+      source_root File.expand_path("../../../../db/migrate", __FILE__)
+
+      def copy_migrations
+        # Use sort() to order the migrations by seq 
+        # Use [2..-1] to delete the seq
+        Dir[ File.join(self.class.source_root, '*.rb') ].sort.each { |f| 
+          copy_migration File.basename(f, '.rb')
+        }
+      end
+
+    protected
+    
+      def copy_migration(filename)
+        if self.class.migration_exists?("db/migrate", "#{filename[2..-1]}")
+          say_status("skipped", "Migration #{filename[2..-1]} already exists")
+        else
+          migration_template "#{filename}.rb", "db/migrate/#{filename[2..-1]}.rb"
+        end
+      end
+    end
+  end
+end