Readme is outdated

[Gargo]

I try examples from your library:

let bytes = Array<UInt8>(hex: "0x010203")  // [1,2,3]
let hex   = bytes.toHexString()            // "010203"

No exact matches in call to initializer

let bytes: Array<UInt8> = [0x01, 0x02, 0x03]
let digest = Digest.md5(bytes)

Type 'any Digest' has no member 'md5'

and etc.