Prepare for release

Update CHANGELOG.md

Add BigInteger::gcdMultiple()

Prepare for release

Prepare for release

Fix BcMathCalculator::divR()

Use 30 max digits by default

This makes calculations much faster, and we may be more likely to find edge cases around the 64 bit limit.

Add tests for BigNumber::of()

Fix bug in Calculator::twosComplement()

The code forgot to prepend the carry bit when all bytes have been zeroed.
This bug affected bitwise operations AND, OR, XOR for all but the GMP calculator.

Revert "Remove deprecated BigInteger::parse()"

This reverts commit 6c37468.
Re-introducing - this should not have been removed in the 0.8 release cycle.