WASMified version

[sjoerdthedev]

Porting Jimp-native to WASM would be very useful as it would:

• Allow people to run jimp-native without having to compile the C++ sources during npm install
• Allow jimp-native to be used within the browser
• Be a bit safer when it comes to memory management

Part of the effort has already been done when moving to lerna, as all C++ code has been separated into a pure implementation and node addon API glue code.