`str(np.array)` is very slow, replaced with `str(np.array.tolist())`, 13x speed increase
`str(np.array)` is very slow, replaced with `str(np.array.tolist())`, 13x speed increase

Timing `variants.get_variants('tomato_snps.chr6-0-100000.bcf', 'SL2.40ch06', 2000, 52000, [])`
Original:
9.59 s ± 205 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)
New:
697 ms ± 2.33 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

nlesc-ave/ave-rest-service