Add parse_pattern_list() function

[RhetTbull]

I am using this in project where I need to match .gitignore patterns but will not be actually reading .gitignore files. (The use case is to match files with same rules as .gitignore but has nothing to do with git. I've added a parse_pattern_list() method to read patterns from a list instead of a .gitignore file to do this. Are you accepting PRs and are you interested in adding this to gitignorefile? If so, I'm happy to submit a PR.