Consider ignoreWhitespace=true parameter to decodeHex

[JakeWharton]

Hex often shows up with visual whitespace (spaces, newlines, tabs). I can preprocess it, and I do, but I've just copied that helper function to my third project.

I think this would be a pragmatic inclusion.

One caveat is that this would probably be a conditional that selected two mostly different implementations of the decoding due to how the current one works.

[swankjesse]

I’m also sad we did a bad job of being consistent with hex and base64. Hex is strict and throws; base64 is lenient and returns null. Whoops!