~jamesponddotco/acopw#1: Inconsistent length in Random.Generate() and PIN.Generate() methods

The Generate method in the Random and PIN structs produces outputs with inconsistent lengths, regardless of the user-defined Length field.

This is likely caused by this section of out code:

for i := 0; i < r.Length; i++ {
	b := randomBytes[i]
	if b >= maxByte {
		continue
	}
	password[i] = charset[int(b)%len(charset)]
}

Need to rewrite the password generation loop to account for skipped characters.