pi_get_years export causes install error

Thanks so much for creating this!  When I try to install the package, I get the following error

`Error: package or namespace load failed for ‘phishr’ in namespaceExport(ns, exports):
  undefined exports: pi_get_years`

It looks like `pi_get_years` is listed in the NAMEPACE, but is not defined in R directory. 

Again thanks!