Package alignment and minor changes.

Hallo Andreas,

Hope you are good. 

1. Aligned groupId and Java packages - `com.scireum.serversass`
2. Moved  `spec` folder into `src / test / resource / spec` and aligned `SassSpecTest` to run together with other tests. It fails now but it will not fail the build.
3. Adjusted README file to use latest Maven configuration.

May I kindly ask you to perform another Maven release when you have time.

Thanks,
Anton