Compatible with Rails 4.1.0, minitest 5

```bash
Run options: --seed 14798

# Running:

.....................I, [2014-02-19T11:37:05.100510 #95528]  INFO -- : missed ids -> [5, 6, 7] | hitted ids -> ["6", "7"]
FI, [2014-02-19T11:37:05.110108 #95528]  INFO -- : missed ids -> [5, 6, 7] | hitted ids -> ["5", "6", "7"]
........

Finished in 0.207117s, 144.8457 runs/s, 207.6121 assertions/s.

  1) Failure:
ActiveRecord::PreloaderTest#test_when_read_multi_missed_from_cache_AR_will_fetch_missed_records_from_db [/Users/jason/work/second_level_cache/test/active_record/preloader_test.rb:26]:
Expected /IN\s+\(5\)/m to match "SELECT \"posts\".* FROM \"posts\"   ORDER BY id ASC\nSELECT \"topics\".* FROM \"topics\"  WHERE \"topics\".\"id\" IN (5, 6, 7)\n".

30 runs, 43 assertions, 1 failures, 0 errors, 0 skips
```

还有个测试没通过，没搞清楚，还得你修复一下。