Rrdf: Release 2.2.1

Egon Willighagen, Ryan Kohl & Carl Boettiger
This release has the following changes: adds (unit) testing with the testthat package adds a tripleCount(store) method some documentation improvements typo in package description now lists all formats in asString() add.data.triple() and load.rdf() should now stop() when exceptions happen (closes #10) add.data.triple() now checks the data type given sparql.remote() now discusses bif:contains (closes #32) now uses missing() instead of is.null() for input checking (addresses #34)