Add travisci configuration file
Merge pull request #23 from ansell/travisci

Add travisci configuration file
rdfa test suite: moved download related methods to the separate helper class
helper method to prepare TestNG data provider output
missed headers
data provider parametrization for integration modules
moved RDFS and XSD vocabs to the semargl-rdf
moved JSON-LD keyword constants to the separate class
added build status info to the README [ci skip]
added tests 330 and 331 from the rdfa test suite
minor NOTICE and RELEASE_NOTES update
test coverage for the NQuadsSerializer
test code deduplication
configured maven-enforcer-plugin
semargl-clerezza dependencies clarification
updated json-ld.org test suite
RDFa test suite update (rdfa/rdfa-website@b10884ec47ade8c38d798443b0606b3e4806e63c)
jsonld: @language nullification support
jsonld: problematic IRI expansion
force terms to be not considered in @id
@reverse for literals