'Create paths recursively, ignore already created dirs
Example:
>>> from lettuce.fs import FileSystem
>>> FileSystem.mkdir(\'~/a/lot/of/nested/dirs\')'

@classmethod
def mkdir(cls, path):

    try:
        os.makedirs(path)
    except OSError as e:
        if (e.errno not in (17,)):
            raise e
        elif (not os.path.isdir(path)):
            raise e
