-----
- Replaced the python package used for parsing GFF/GTF files. It used to be
bcbio-gff and is now gffutils.
- Added the "-S"/"--sum-on-duplicate-id" flag. When this flag is set and a
given table contains multiple rows with the same feature id, then the
value in the output table will be the sum of the values from each of
those rows.
- Added a warning message when a feature is encountered multiple times in a
table