Escape directory names when creating album

[neanton]

Albums containing forward slashes are not created properly. When such album is processed OSError: [Errno 2] No such file or directory rises.
OSX does not allow slashes in file/directory names so it would be better to replace them with something like a . or _ char.

https://github.com/amka/Spelt/blob/master/spelt/__init__.py#L217

[amka]

Fixed in 0.2.1