improve support for multi-part encryption/decryption

[fuzzykat]

• implement encryptUpdate, encryptFinal methods
• implement decryptUpdate, decryptFinal methods
• add multi-part encryption/decryption tests

[coveralls]

coverage: 86.864% (+0.3%) from 86.582%
when pulling 3024de1 on fuzzykat:feature/decrypt_update
into 3386f93 on LudovicRousseau:master.

[LudovicRousseau]

Looks good to me.

Can you:

• split the commit in 2 for implementation and test
• include the "[pre-commit.ci] auto fixes from pre-commit.com hooks " commit in the 2 commits described above

[fuzzykat]

* split the commit in 2 for implementation and test

* include the "[pre-commit.ci] auto fixes from pre-commit.com hooks " commit in the 2 commits described above

Done.

[LudovicRousseau]

Thanks