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* Fix Python3 issues
* Added sequence functions: complement(seq) and translate(seq)
* Added fasta write function: fasta_dict_to_file(fasta_dict, fasta_file, line_char_limit=None)
* Added Gff method to return the sequence of line_data: sequence(self, line_data, child_type=None, reference=None)
* Gff.write no longer prints redundent '' when the whole gene is marked as removed