DS-460 Always round down human readable count

@sergii-tkachenko Can you please review?

Won't display 3 million until we actually got the 3 million.

Closes https://jira.dosomething.org/browse/DS-460
Sorry, this one was my fault. I missed that in [`pow()`](http://php.net/manual/en/function.pow.php) the first argument is number, so power return zero in any case.