`splice` throws error if directory is empty
don't use system.file, doesn't seem to work when building package
Roxygenize
Bump version to 0.0-2.1
Update NEWS.Rd
store and row names in a separate file, retrieve them unconditionally; implement function row.names

Fixes #1.
Roxygenize
Bump version to 0.0-2.2
Update NEWS.Rd