Add support for circularly permuted sequences in `deduplicate`

[apcamargo]

A pair of identical circular sequences can differ only in their breakpoints. In the example below, the two sequences are identical when treated as circular, but their breakpoints differ:

>seq_a
CGAAACGTTCTT
>seq_d
GTTCTTCGAAAC

As a result, they produce different hashes. To enable vclust deduplicate to detect this scenario (for example, through a --circular option), a lexicographically minimal string rotation algorithm could be used to normalize breakpoint positions in circular sequences. I implemented this approach in seq-hasher here.