Addtped

As discussed!
When parsing a VCF using vcfnp, the default arity for the ALT field is 1, meaning that the variants['ALT'] array will be a simple one-dimensional array of strings. However, it may be that the arity for the ALT field was set higher to capture multiallelic variants, e.g., for Ag1000G the ALT field has arity 3, which means in that case the variants['ALT'] array has shape (n_variants, 3). The anhima.io.save_tped() function expects a one-dimensional array for its 'alt' argument, so I think you need to add a check here to see if ALT is 1D or 2D, and if 2D then slice it so you pass through only the first column. E.g.:

```
genotypes = np.take(calldata['genotype'], inc_samples, axis=1)
ref = variants['REF']
alt = variants['ALT']
if alt.ndim > 1:
    alt = alt[:, 0]
anhima.io.save_tped(path, genotypes=genotypes, ref=ref, alt=alt)
```

(Also for some reason using `np.take(a, idx, axis=1)` is faster than `a[:, idx, :]` even though they do the same thing.)