bombing when providing a list of NHDPlus files

I pulled today which brought me up to 2e44c8e6a9. For some reason, SFRmaker can't parse a list of multiple folders for NHDPlus, although that worked in the past.

traceback is like:
``` File "/Users/mnfienen/Documents/GIT/SFRmaker/sfrmaker/lines.py", line 600, in from_nhdplus_v2
epsg=epsg, proj_str=proj_str, prjfile=prjfile)
File "/Users/mnfienen/Documents/GIT/SFRmaker/sfrmaker/nhdplus_utils.py", line 116, in load_nhdplus_v2
crs = get_shapefile_crs(NHDFlowlines)
File "/Users/mnfienen/Documents/GIT/gis-utils/gisutils/shapefile.py", line 385, in get_shapefile_crs
basename, ext = os.path.splitext(shapefile)
File "/Users/mnfienen/miniconda3/lib/python3.7/posixpath.py", line 122, in splitext
p = os.fspath(p)
TypeError: expected str, bytes or os.PathLike object, not list```