Update java library

[polvallverdu]

Hey, A while back I forked the original Java nanoid library (jnanoid), since optimizations and improvements could be made:

• Security Issue: Remote code execution could be ran.
• Random Security: Java's more secure Random wasn't being used.
• Better Unit Testing
• More useful methods

In the readme the recommended Java Library is still pointing to the discontinued one. I've updated it.

[ai]

Thanks for keeping that project alive!