Added type specific argbinsearch functions to perform binary search via a
permutation array. `fastsearchsorted` now supports the same functionality
as `searchsorted`. No tests being run on it though.

Need to do more benchmarking, but a direct binary search on floats runs
~1.4x faster for large needles, and peaks at about ~3.5x for some
intermediate needle sizes (100-500 depending on haystack size). For
indirect binary searches, the values are more like 1.2x and 2.5x.

For ints, direct searches can be up to ~2.5x faster, the speed increasing
with both the size of the needle and the haystack. Indirect searches are up
to ~1.6x faster for large needles and haystacks.