Locate public URL for gencode gtf file

[jpdna]

The file

gencode.v19.annotation.gtf.gz

from solveBio S3 turns out to not be identical to:

ftp://ftp.sanger.ac.uk/pub/gencode/Gencode_human/release_19/gencode.v19.annotation.gtf.gz

We need to determine if either this file was post-processed after download or if a matching version is available for download from the gencode project.

@dandanxu could you take a look at this?

[dandanxu]

loooking into this

[dandanxu]

to be honest, i'm still not sure. It looks like the spacing is occasionally occasionally different but otherwise the data looks the same. In any case, I don't think this matters toooo much - we don't use actually use these files anywhere since we stopped actively supporting ensembl transcripts in favor of refseq transcripts (at one point we supported both, but we haven't for quite a while and it won't work without a bit of tweaking). Probably just focusing on refseq is good for now, since that's the harder case, and hopefully UTA integration will take care of ensembl =).