Factor timing implementation out of SoftwareResult

This is a small refactor of the `_faster_get` method in `Genome::SoftwareResult`. It removes the timing implementation from the method and cleans up the metric name generation slightly.
Totally unrelated to this PR...

I'm always bothered by having to copy something on one line and then mutate it on the next.  I still haven't found a style I like that we can use, but in Perl 5.14 they added a non-destructive option to `s///` such that you could do,

```
my $statsd_class_suffix = ($class =~ s/::/_/gr);
```

I don't know if I really like this but this works on older Perls and hides the mutation better,

```
my ($statsd_class_suffix) = map { s/::/_/g; $_ } "$class";
```

Like I said, not related to this PR.  This line just reminded me of it.