Add db migrate task

Rakefile

@@ -22,4 +22,17 @@ Rake::TestTask.new do |t|
   t.verbose = true
 end
 
+namespace :db do
+  desc 'Run database migrations'
+  task :migrate do
+    Sequel.extension(:migration)
+    db = Sequel::DATABASES.first
+    dir = App.root.join('db/migrate')
+    opts = {}
+    opts.update(target: ENV['VERSION'].to_i) if ENV['VERSION']
+
+    Sequel::IntegerMigrator.new(db, dir, opts).run
+  end
+end
+
 task :default => [:test]