Custom URL parameter for "python -m unidic download"

[JackLawrenceCRISPR]

The following command is an example of how to use this change:

python -m unidic download "3.1.0+2021-08-31" "https://cotonoha-dic.s3-ap-northeast-1.amazonaws.com/unidic-3.1.0.zip"

I made two changes to the codebase:

1. The unidic download command can now accept a URL argument due to a small change in the "download_version" function code. The original behavior is unaffected.
2. The README.md documentation has been updated to explain how to specify custom "ver" and "url" parameters with an example.

[kneo]

I second this, in addition:

If you want to use the official mirror, the script will fail because the archives use Deflate64
https://clrd.ninjal.ac.jp/unidic/en/

suggest to add, dependency:

zipfile-deflate64

and:

import zipfile_deflate64 as zipfile

instead of

import zipfile

in download.py to fix this exception.