added JUnit dependency to pom.xml
minor changes R2RML-to-SML converter

- added a helper method that will be needed for testing
- changed how the view definition name is extracted from a triples map
  Previously the view definition names were built using a combination of
  the logical table and the triples map URI which can not be used due to
  syntax restrictions of the SML. Thus the local part of the triples map
  URI is used for now.
closes #3

- copied the tests from the Sparqlify-Extensions repo over and made them
  pass