minor tweaks

Clarifying some (random) things that are incomprehensible to english
speakers who don't live in an American context, or otherwise seem
unnecessarily cryptic
typo

Thanks M. Corlosquet
Documenting release history.
Drafting a releases page.
Added earlier info.
Linked more terms, dated workPerformed.
Added 0.91.
Linked the releases page.
Added IDs and reworded note at footer.
Fixed markup, css, numbering.
Merge pull request #79 from danbri/sdo-releases

Adding a Schema.org Releases history page.
Linked LOV.
Merge pull request #74 from chaals/master

minor tweaks
Add periodical equivalence assertions for bibo

A number of the periodical properties and classes have clear equivalence
to Bibliographic Ontology Specification (bibo) counterparts.

While many of the classes and properties emerged organically, in the
case of pageEnd, pageStart, and pagination the properties were derived
directly from bibo; acknowledge that accordingly.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Merge branch 'master' of github.com:dbs/schemaorg into periodical_position
Enable tests to pass by adding a Unit.storePrefix() method

Currently the method does nothing, but parsers.py expects to be able to
call it when it encounters a prefix attribute when parsing
data/schema.rdfa, so let it at least not fail.

Signed-off-by: Dan Scott <dan@coffeecode.net>
Use fully expanded URIs for equivalentProperty

Rather than messing around with prefix attributes and the parser,
fully expanded URIs just work. So let's go with that.

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