Add guard-rspec and basic Guardfile
Make `guard` less chatty
Refactor Vocabulary using class instance variables.
This fixes issue #153.
Merge branch 'peter_v-add-guard/01' of https://github.com/petervandenabeele/rdf into petervandenabeele-peter_v-add-guard/01
Merge branch 'petervandenabeele-peter_v-add-guard/01' into develop
Merge remote-tracking branch 'origin/develop' into develop
Change RDF vocabulary to delegate to RDF::RDFV, allowing definitions for RDF properties, classes, datatypes along with comments and labels.
This partially addresses issue #159.