Find common words between grouping variables (e.g., people).
common(word.list, overlap = "all", equal.or = "more", ...)A list of named character vectors.
Minimum/exact amount of overlap.
A character vector of c("equal", "greater", 
"more", "less").
In lieu of word.list the user may input n number of 
character vectors.
Returns a dataframe of all words that match the criteria set by 
overlap and equal.or.