Sphinx: Improve doc strings

[buhtz]

I'm not a Sphinx fan so I'm not able to give you an advice how to solve this.

But please see that this HTML output
https://randomfiletree.readthedocs.io/en/latest/core.html#randomfiletree.core.iterative_gaussian_tree

doesn't fit to the original docstring

RandomFileTree/randomfiletree/core.py

Lines 114 to 134 in 4e3df78

	Args:
	basedir: Directory to create files and folders in
	nfiles: Average number of files to create
	nfolders: Average number of folders to create
	repeat: Walk this often through the directory tree to create new
	subdirectories and files
	maxdepth: Maximum depth to descend into current file tree. If None,
	infinity.
	sigma_folders: Spread of number of folders
	sigma_files: Spread of number of files
	min_folders: Minimal number of folders to create. Default 0.
	min_files: Minimal number of files to create. Default 0.
	filename: Callable to generate filename. Default returns short
	random string
	payload: Use this argument to generate files with content: Specify a
	function that takes a directory ``dir`` (``Path`` object) as
	argument, picks a name ``name``, creates the corresponding file
	``dir/name`` and yields ``name``. Overrides ``filename`` argument
	if both are passed. Takes Path object as catalog where to create
	file and returns Path of created file.
	If this option is not specified, all created files will be empty.

Not all arguments are recognized as arguments.