Better Java 9+ compatibility and improved documentation

• removed dependency on DatatypeConverter which has been removed from Java 9+ JREs
• improved documentation in README.md

0.0.4

• minor performance enhancements
• removed commons-lang3 dependency
• updated maven build chain

Improved interface, performance improvements and better test coverage.

1. added support for hashing byte arrays and static constructors
2. cache hash digest
3. implemented equals and hashCode
4. compare now uses the much faster Integer.bitcount method
5. added bitwiseDifference which yields the number of bits that differ between hashes
6. improved test coverage
7. code cleanup