Browser hex encoder refresh

[jimhark]

Summary

Freshen up the browser version of HexEncoder

Resolves

resolves #220

Details

• parse()
  • simplify var names
  • Minor reformatting
  • Throw Error() object, not string
• stringify()
  • Pad hex using .padStart(2, "0")

Testing

I manually tested node encrypt, node decrypt, and HTML wrapper decrypt.