Documentation for ConceptNet 5.1 is up

[Rob Speer]

I've updated the wiki to document ConceptNet 5.1:
https://github.com/commonsense/conceptnet5/wiki

This will be especially useful for those who are looking for a
downloadable version. Note that the representation is different from
5.0 in a very significant way, which is that assertions are now
primarily represented via edges, not nodes. The system where
assertions were nodes, with edges pointing out of them to their
arguments, was too difficult to use.

However, assertions can still be reified as nodes when they need to be
-- in particular, when there are assertions about assertions. We now
have some of those, because we've included the translations of entire
ConceptNet assertions between languages that were collected by the
GlobalMind project.

My next step is to put up and document a new API for ConceptNet 5.1.
-- Rob