Add travis configuration

I've also added a travis CI configuration file, as well as fixed the tests to pass under Ruby 1.8 (should use hash rocket syntax for hashes).

Once you've accepted the pull, you'll need to log in to http://travis-ci.org and then enable the service hook for the project.

Finally, you can add the travis build status image to the README.rdoc:

```
{<img src="https://travis-ci.org/evan/memcached.png" alt="Build Status" />}[https://travis-ci.org/evan/memcached]
```

Thanks for accepting all my previous pulls!