Chromosome names can exceed 6 characters

[adthrasher]

Limiting chromosomes to 6 Unicode characters does not work for chromosomes such as chrUn_KI270747v1.

SICER2/sicer/src/separate_bedpe_chroms.py

Line 21 in 002b59d

read_dtype = np.dtype([('chrom', 'U6'), ('start', np.int32), ('end', np.int32), ('name', 'U20'), ('score', np.int32), ('strand', 'U1')])