Initial support for external processes
Initial support for external processes

The open() function now tries to spawn external processes if
'external=True'. If 'parallel=True' is also specified, multi-threaded
external programs will be used. If external programs are not found,
open() will silently try alternatives instead.

The supported external programs are gzip, bzip2, xz, pigz, and pbzip2.

wbolster/zseqfile