Add benchmark for find() algorithm

[kylelutz]

Add a benchmark for the find() algorithm (i.e. perf_find).

See the perf/perf_count.cpp benchmark for an example/template.

It would also be good to add a corresponding benchmark for the STL std::find() algorithm (i.e. perf_stl_find).

[Mageswaran1989]

I will give a try

[jszuppe]

I may be closed. See #444.

[kylelutz]

Closed. Thanks!