started adding a test for freqdist calculation;
modified generate_freqdist to optionally return the freqdist as a dataframe
Merge branch 'feature/hot-topic-of-the-day' of github.com:NAMD/mediacloud_backend into feature/hot-topic-of-the-day
Added test for fetching documents of a given day;
tests passing
Added test for fetching a document's freqdist from PyPLN
Finished basic implementation of hot topic of the day;
Added test.