Extends BED regions (5' and 3')

Usage: bedutils extend {opts} bedfile

Options:
    -5 SIZE     Extend the region SIZE bases in the 5' direction
    -3 SIZE     Extend the region SIZE bases in the 5' direction

SIZE is how much the region should be extended in the corresponding
direction. If the first character of SIZE is '=', then the region is
extended in the corresponding direction and the length of the region
is set to be exactly SIZE. Only one direction is allowed when SIZE
starts with "=".

Note: using an exact size may make a region smaller!