Allow AAP to be non integer

[RosCraddock]

Small updates to input the alt_allele_prob_file as a float rather than an integer (which is then turned into a float). This now allows the inputting of decimals such as 0.5, 0.45 which previously caused a valueError.

[RosCraddock]

Apologies, I forgot to tag. @gregorgorjanc and @XingerTang, please review when you can.

[gregorgorjanc]

@RosCraddock I don't think we need the nonInteger argument here - we just need to pass the dtype as a float and not as an integer. And dtype should likely be float by default anyhow as we work with probabilities in AlphaPeel. OK?

[XingerTang]

@gregorgorjanc Normally that function only takes sequence and genotype input so it is originally designed for the integer inputs.

[gregorgorjanc]

I see. Couldn't we then stick to dtype arg only (not adding the nonInteger arg) and if we pass in a np.float type then we avoid using the int() (as done in this PR)

[RosCraddock]

@gregorgorjanc you're right! I can make the conditional statement on line 67 using the dtype instead.

[gregorgorjanc]

LGTM!