first version of tests for expected RDF

it addresses #17 

not fully ready to merge but i would like to get some feedback, and discuss travis-ci integration
you can test it by running from root of the repository

```shell
$ npm install
$ npm test
```

i could also setup separate repository and run those tests independently!
Great work @elf-pavlik Would be great to see if we can also leverage this to convert the examples in the Hydra spec to Turtle.