provide analogue of `@elapsed`

[stevengj]

A lot of times, I just want the minimum time, especially if I'm collecting or comparing a lot of timing measurements. It would be nice to have an analogue of @elapsed that just returns the minimum time, but with all of the @benchmark niceties.

I've been using:

"""
Like `@benchmark`, but returns only the minimum time in ns.
"""
macro benchtime(args...)
    b = Expr(:macrocall, Symbol("@benchmark"), map(esc, args)...)
    :(time(minimum($b)))
end

Could something like this be included?