I think the range encoded by the ASCII encoding of Phred scores is [0, 94), and this is checked in the `toChar` method. Should we also limit our internal QualityScore representation to that range? Doesn't bother me, since we can always change it later if it turns out that 93 isn't high enough, but I'm just wondering since there's no physical, computational, nor mathematical reason for the cutoff of 93.