CFB mode segmentSize bug fix

[shanmukhateja]

Fixes #29

[sw6ueyz]

Please check your code again.
It will completely disable segment size validation since (n * S) % S === 0, the error will never occur.
It seems like the fix should be something like this:

if ((plaintext.length * 8) % this.segmentSize !== 0)

[shanmukhateja]

Hi @sw6ueyz

I do not remember why this change was needed and frankly I do not need it anymore.

Feel free to make changes as you see fit. I won't be able to help with this. It's been 5 years :)