Add RDFS for type and attribute pages

Includes properties such as:
* rdfs:comment
* rdfs:label
* rdfs:subClassOf

With this patch, individual type and attribute pages will now express basic
RDFS; classes will express their immediate subclass relationship and all
of the properties that can be applied to them, while attributes express
their domainIncludes values.

Addresses #24

Signed-off-by: Dan Scott <dan@coffeecode.net>
Clarify that RDFa and JSON-LD are supported formats

The getting started documentation referred to a long-term plan to
support a broader variety of formats, but RDFa and JSON-LD are
pretty tightly integrated into the rest of the schema.org documentation,
so we might as well mention them explicitly in the getting started (but
continue documenting with microdata as the default approach).

Signed-off-by: Dan Scott <dan@coffeecode.net>
Merge pull request #41 from danbri/master

Fix Question examples to use 'upvoteCount' instead of mistaken 'voteCount' property.
Merge pull request #29 from dbs/gs_broader_serialization

Clarify that RDFa and JSON-LD are supported formats
Merge branch 'per_page_rdfs' into newmerge

Signed-off-by: Dan Scott <dan@coffeecode.net>

Conflicts:
	api.py
Merge pull request #25 from dbs/per_page_rdfs

CODE: Add RDFS for type and attribute pages
Merge branch 'master' into sdo-itemlist