Adding some tests

I used your gem and found it very helpful. In the process of debugging some issues in regards to performance I added a few tests to help track things down.

I don't know if this is useful but to run tests, after a bundle install.

```bash
rake test
```

I added minitest, mocha and a copied version of memcached_mock to the project. I used mimitest and mocha because Dali includes the same versions but I couldn't find a way to use memcached_mock without copying the file over.