v0.4.2

• matUtils extract includes --write-taxodium option to output taxodium-compatible protobuf files viewable on the web browser.
• Improvements to matUtils introduce.
• New masking routine which performs local or global masking of mutations
• ARM support in matOptimize with a new tree drifting option.
• A few more bug fixes and directory structure cleanup.
• Fixed the logic of getting the nearest subtree.