Attempt to find the project root, returns None if not found

def find_project_dir(path=os.getcwd()):
    """Attempt to find the project root, returns None if not found"""
    path_split = os.path.split(path)
    while path_split[1]:
        if in_armstrong_project(path):
            return path
        path = path_split[0]
        path_split = os.path.split(path)
    # we ran out of parents
    return None