make auto_open default to stdin/stdout when path evaluates to False

[golobor]

[agalitsyna]

Resolved in b002dbe with some additional improvements, such as default to stdin/stdout when "-" found instead of path.

How about transfer to this nice class, which might further simplify this?

pairtools/pairtools/_fileio.py

Lines 139 to 149 in 254695a

	class PipedIO:
	def __init__(self, file_or_path, command, mode='r'):
	"""
	An experimental class that reads/writes a file, piping the contents
	through another process.
	Parameters
	----------
	file_or_path : file-like object or str
	A path to the input/output file or an already opened
	file-like object.