v0.5

Changelog:

* Change pgxo:causes to a set of potential relationships, adding more granularity
* Remove subclass axiom based on sets of associated components for PharmacogenomicRelationship
* Update documentation accordingly

Version 0.4 of PGxO

Changelog:
* New base URI
* Update documentation accordingly
* Add HTML documentation of the ontology

Version 0.3 of PGxO

Minor change in README