Add configurable hash mod base

[jchennales]

When generating hashes that are separated by 100 the hash strings are very similar. This is unavoidable with this implementation and perhaps not a huge deal, but maybe it would be best if the periodicity were a number that is not so "tidy". This PR adds the ability to construct the class with a user-specified hash mod base. I personally would use a similarly large prime number, like 97. The strings are very similar for every 97 ids, but this is probably less likely to be noticed.

Also increase JUnit 4 version to avoid CVE flagging