Old SNAP version doesn't work with large genomes

[dnieuw]

While building the reference db SNAP gave me this error message in the err log:
"This tool only works with genomes with 2^32 bases or fewer "
According to this thread: https://groups.google.com/forum/#!msg/snap-user/yUsYA6p4Loo/Rb729x-qCVcJ this error occurs only in older versions of SNAP. I downloaded version beta18, which seems to fix the problem. You might want to update the installation script to include the newer version of SNAP.