Updated formats.gff.format() with options to remove specific feat types
and Parent links to that feature entry, option to verify feature type
against SO; Added in GffLine.get and set_attr to help with easily retrieval
and update of an attribute in a GFF3 line; Moved verify_term() from
formats.agp to formats.obo; Added a `strict` flag to
formats.base.DictFile() to decide if program should exit when a
DictFile() does not have more than 2 columns of data or just skip
that line