Minor refactorings w/ tests

I had a close-to-the-wire release with 10 minutes to spare which hasn't yet shown up as acknowledged, and I wasn't sure if it was a code bug or not.

So I factored out some of the components into `lib/` and wrote some tests for it.

The METACPAN data seems to indicate I was under: 
```
 perl -MCPAN::Distribution::ReleaseHistory -E' say scalar gmtime CPAN::Distribution::ReleaseHistory->new( distribution => q[Dist-Zilla-Plugin-MetaProvides-Package], scroll_size => 1 )->release_iterator->next_release->timestamp'
# Mon Jul 28 23:50:42 2014

```

And the raw value of timestamp I've used in the test at [R47](#diff-2581be229937c2ee51c13c225583dacaR47) and it looks fine, so I'm just guessing your data source hasn't updated yet.