Add namespace and test

This is much more extensive as things have been moved around for `PSR-4` autoloading which is why I wanted a `develop` branch and to have the current implementation tagged.

I've renamed the class to `socrata\soda\Client` to better match the other libraries.  Also, I did have problems testing the `POST` and `PUT` actions, so the test is currently very 'happy-path'.  Any suggestions for making it more robust are welcome.

Lastly, this should lay the foundation for extending the library with more robust `SoSQL` support.