Cache indicators that were successfully sent to avoid dups.

def cache_items(values):
    """Cache indicators that were successfully sent to avoid dups."""
    import os
    config_path = os.path.expanduser('~/.config/blockade')
    file_path = os.path.join(config_path, 'cache.txt')
    if not os.path.isfile(file_path):
        file(file_path, 'w').close()
    written = [x.strip() for x in open(file_path, 'r').readlines()]
    handle = open(file_path, 'a')
    for item in values:
        # Because of the option to submit in clear or hashed, we need to make
        # sure we're not re-hashing before adding.
        if is_hashed(item):
            hashed = item
        else:
            hashed = hash_values(item)

        if hashed in written:
            continue
        handle.write(hashed + "\n")
    handle.close()
    return True