rvertnet v0.8.3

MINOR IMPROVEMENTS

• new maintainer (#71)
• fix CI
• refresh test fixtures (#71)
• remove plyr from examples
• refresh Darwin core terms and move to data object
• refresh vignette and its pre-compilation
• update Makefile
• update roxygen2 and documentation fixes
• remove outdated files

BUG FIXES

• fix class handling in vertmap to allow tibble input
• allow vignette to build
• fix ggplot2 deprecation warning (#71)