Small upgrade

Hello,

Thank you for this excellent plugin!

I only saw one problem with counting free memory percentage for values like 800KB or something less. I think that you need to change Bytes to Mega Bytes after calculating percentage value.
So I moved line:
my $mem_free_perc = int(($mem_free / $mem_total) * 100);
above:
$mem_used = int($mem_used / 1024 / 1024);
$mem_free = int($mem_free / 1024 / 1024);
$mem_total = int($mem_total / 1024 / 1024);
And now it works perfect!