[Biopython] GFF3Writer

[Brad Chapman]

Michal;

> Thank you it works. How is it possible to create ##sequence-region
> with the writer like described in
> http://www.sequenceontology.org/gff3.shtml:
> 
> ##gff-version   3
> ##sequence-region   ctg123 1 1497228
> ctg123 . gene            1000  9000  .  +  .  ID=gene00001;Name=EDEN
> ctg123 . TF_binding_site 1000  1012  .  +  .  Parent=gene00001
> ctg123 . mRNA            1050  9000  .  +  .  ID=mRNA00001;Parent=gene00001

Thanks for the feedback. I added in support for this directive if
you pull the latest version from GitHub:

https://github.com/chapmanb/bcbb/tree/master/gff

This will work as long as you have a sequence specified for the
record. Let me know if you run into any problems,
Brad