Added a KeywordArticle class to store data about sums for keyword occs and tokens subset by year for each article. The script now uses that class as a data structure.
Added another check: Check article with unigram last name and then bigram full name. List articles in the diff of those sets. Andrew asked to do it for Herman Melville only but the script is parametrized so it can easily be run for any other author in the future.
Minor change to the code to avoid article names with commas in them. This messes up the display when outputting to a csv file. Commas in article names are replaced by semicolons