[fix]: convert select columns to list

[vpchung]

Fixes #43

Changelog

• add a new function: convert_to_stringlist() that will accept a Pandas series, replace all instances of , (trailing space) with , (no space), then split the string by ,
• convert the following columns to a list prior to syncing:
  • Publication Assay
  • Publication Tumor Type
  • Publication Tissue
  • Publication Grant Number