Include an example of how to download over http in README

[yeban]

No description provided.

[sjfranklin]

I don't have the ability to test the FTP (normal) download method. Someone who can check both methods can hopefully confirm the following:

ncbi-blast-dbs nt
Downloads databases using normal method

ncbi-blast-dbs http nt
Downloads using http.

For the latter, I get this expected output:

using http-ncbi-dbs-dgs.rake
using http method
wget -Nc --no-verbose ftp.ncbi.nlm.nih.gov/blast/db/nt.00.tar.gz

[yeban]

Yeah, that's correct - I tested both the day I merged.

The reason to ask you was that I thought you may want to anyway as you added the functionality