Set IRIs

[dosumis]

consist_of --> iri": "http://purl.obolibrary.org/obo/RO_0002473", "label": "composed_primarily_of"
subcluster_of -> iri: "http://purl.obolibrary.org/obo/RO_0015003", "label": "subcluster of"
cluster --> iri: http://purl.obolibrary.org/obo/PCL_0010001", "label": "cell cluster" # This one might change

[dosumis]

Would like to fix before release.

[ubyndr]

Implemented this change in the #34 with d49e670

[ubyndr]

This has been resolved with #34