Complete gem restructure

* Travis, Coverall, Pry and Guard added following [this](http://www.smashingmagazine.com/2014/04/08/how-to-build-a-ruby-gem-with-bundler-test-driven-development-travis-ci-and-coveralls-oh-my) guide.
* Nokogiri and [semantic_crawler](https://github.com/obale/semantic_crawler) approach completely changed.
* Endpoint changed, response returned is formatted in Terse RDF Triple Language ([Turtle](http://en.wikipedia.org/wiki/Turtle_(syntax))), similar to SPARQL.
* [linkeddata](https://github.com/ruby-rdf/linkeddata) gem added to fetch a RDF [repository](http://rubydoc.info/github/ruby-rdf/rdf/RDF/Repository) and [query](http://rubydoc.info/github/ruby-rdf/rdf/RDF/Queryable:query) for data.
* Tests cases added.