Find regions of first bed file that overlap regions in a second bed file. The
output preserves all fields from the input.
+NOTE: -u and -d options are currently not functional!
usage: %prog bed_file_1 bed_file_2
-m, --mincols=N: Require this much overlap (default 1bp)
-u, --upstream_pad=N: upstream interval padding (default 0bp)