Fixes for original sequel adapter

There was an attempt to write sequel adapter in #1030. I took commits
from this PR. This commit fixes most of the failures that are result of
applying these commits into much newer codebase. Most of the code is
also copied from the original PR.

Author: lukesarnacki

Rakefile

@@ -15,6 +15,10 @@ namespace :test do
   Rake::TestTask.new(:benchmark) do |t|
     t.pattern = 'test/benchmark/*_benchmark.rb'
   end
+  desc "Refresh dump.sql from fixtures and schema."
+  task :refresh_dump do
+    require_relative 'test/support/database/generator'
+  end
 end
 
 desc 'Test bug report template'

jsonapi-resources.gemspec

@@ -29,6 +29,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'sequel'
   spec.add_development_dependency 'sequel-rails'
   spec.add_development_dependency 'activerecord', '>= 4.1'
+  spec.add_development_dependency 'database_cleaner'
   spec.add_dependency 'activesupport', '>= 4.1'
   spec.add_dependency 'railties', '>= 4.1'
   spec.add_dependency 'concurrent-ruby'