v4.2

This is a fairly minor release, fixing a couple of small issues.

Changes

• The Corax+ test now properly tests both calling and returning, as well as BCD with values that result in one or two digits, thanks to @GamingMadster (#22)
• The README has once again been improved, thanks to @greg-kennedy (#20) and feedback from @algometric (#19)
• The quirks test now tests the memory quirk for reading and writing, not just writing. Thanks to @gfcwfzkm for reporting this issue (#21)