Stop shifting from extending past genome boundaries
Stop shifting from extending past genome boundaries

When provided with a genome file, shift was still creating
intervals that extended past the last base pair.
See issue #599.

jmarshall/bedtools2,arq5x/bedtools2,arq5x/bedtools2,jmarshall/bedtools2,arq5x/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,arq5x/bedtools2,arq5x/bedtools2